ASME Conference Presenter Attendance Policy and Archival Proceedings

2018;():V008T00A001. doi:10.1115/OMAE2018-NS8.

This online compilation of papers from the ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering (OMAE2018) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Polar and Arctic Sciences and Technology: Arctic Sea Transportation

2018;():V008T07A001. doi:10.1115/OMAE2018-77396.

The most urgent task in tapping of the Arctic resources today is organization of year-round navigation through the Northern Sea Route. The efficiency of any transport system strongly depends on the deadweight and speed of cargo carriers. In this connection it is required to thoroughly examine the issues related to propulsion of large-size cargo ships in ice, while developing the tactical planning and operation control technologies for icebreakers and ice-going ships. It is found that large-size cargo ships are not able to navigate independently in ice at economically efficient speeds even if their hullform is optimized for these operating conditions. Thus, it is required to ensure their effective operation in ice channels made by icebreakers. For appraising the efficiency of a marine transportation system it is necessary to have data on ship resistance versus a range of factors including physical and mechanical properties of ice, ice concentrations, ship speed, etc. This paper presents the results of studies undertaken to examine various methods of icebreaker-assisted shipping operations and to develop a method for calculation of ship resistance in ice channel based on model test data. The research was supported by RSF (project No.17-79-20162).

Topics: Ice , Ships
Commentary by Dr. Valentin Fuster
2018;():V008T07A002. doi:10.1115/OMAE2018-77802.

Due to the dynamic development of the oil and gas fields in the Arctic, the challenges of supply fleet sizing and composition in this region are becoming relevant. In most studies, the Arctic is mainly associated with ice conditions, but it is not the only factor that influences the design of platform supply vessels (PSV) and corresponding marine transport systems (MTS) for this region. The structure of cargo flow (i.e. its distribution by cargo types) affects the supply system significantly. It defines the level of utilization of vessel capacity that determines transport efficiency. At the same time, the literature represents this aspect poorly.

This paper describes an approach to optimize supply fleet configuration by the criterion of total cost considering both non-stationary ice conditions and structure of cargo flows. The cargo-flow-oriented design concept incorporates the detailed calculation model of PSV and the special tactical planning algorithm. PSV model allows considering the influence of cargo spaces on the main characteristics and operational parameters of the ship. It covers the main design aspects of PSVs: general arrangement; lines plan; resistance in open water and ice; engine and propeller characteristics; hydrostatics; capacity and mass calculation. The pseudo-optimal tactical planning algorithm is intended to build the plan of voyages and to set the size of fleet considering the structure of cargo flow.

As the test example, we examine a task of servicing the group of platforms in the Kara Sea. The case study shows that cargo flow structure has a high influence on the efficiency of PSVs in case of high-load operation; while a widespread “deck-cargo” approach is unable to consider this aspect because it ignores the vessel’s carrying capacity and payload. The conclusion about a higher efficiency of PSV compared to AHTS with the same displacement was drawn.

Commentary by Dr. Valentin Fuster

Polar and Arctic Sciences and Technology: Full Scale Measurements and Ice Model Tests

2018;():V008T07A003. doi:10.1115/OMAE2018-77043.

In this paper, ice model tests with different lengths of parallel middle-body were conducted to estimate accurate resistance performance of ice-breaking merchant vessels. Totally, three model ships were manufactured: The standard vessel is 90,000 DWT tanker to transport oil in the ARC7 condition, and two vessels have only different lengths of parallel middle-ship compared to the standard vessel. Ice breaking, ice friction, ice buoyancy, and open-water resistances were classified and measured in experiments, and each resistance component according to change of ship’s length is analyzed. In addition, the resistance formula of ice-breaking tanker is developed by a regression analysis.

Topics: Ice , Tankers
Commentary by Dr. Valentin Fuster
2018;():V008T07A004. doi:10.1115/OMAE2018-77210.

Propulsion performance of icebreakers cannot be calculated as per the classic system of propeller-hull interaction coefficients due to high negative values of wake fractions. To overcome this difficulty, this paper applies an alternative system of propeller-hull interaction coefficients. This system consists of thrust deduction fraction, coefficient of hull effect upon thrust and coefficient of hull effect upon torque.

The method suggested in this paper was used to analysis the data of ice trials for Vladivostok and Novorossiysk icebreakers. The input data in this analysis are speed in the ice field and required power. The sought values are propeller rotations per minute (RPM) and ice resistance. Propeller RPM values are compared versus the results of full-scale ice trials. Ice resistance values are compared versus the predictions based on the model test data obtained in ice basin of Krylov State Research Centre (KSRC).

It is shown that at low speeds in the ice field (0.5–5.0 knots), calculated propeller RPMs have good correlation with the full-scale measurement data.

This paper also gives propulsion performance calculation for Vladivostok icebreaker in 1.5-m thick ice field.

Topics: Propulsion , Ice , Propellers , Hull
Commentary by Dr. Valentin Fuster
2018;():V008T07A005. doi:10.1115/OMAE2018-77638.

Recently, the research activities by domestic and overseas researchers using the Korean ice-breaking research vessel, ARAON have been actively conducted. The ARAON regularly operates for research activities in the Antarctic and the Arctic Ocean every year. She conducts many scientific and engineering tasks including ice load measurement, investigation of the properties of material strength for sea ice, and icebreaking performance test during her voyages. Such tests provide important data for studying icebreaker.

Ice-breaking mode is determined by conditions of sea ice and ice field, and it is divided into ramming and continuous icebreaking. When the icebreaker meets thick ice or icebergs, the ramming is conducted. At that time, the ship speed is generally slower than that of the continuous icebreaking. The ARAON conducted icebreaking performance tests at the Amundsen Sea in Antarctica in 2012. Many strain data were measured in the ramming and the continuous icebreaking.

This study was based on the strain gauge signals measured by the ARAON during the research voyage in 2012 in the Antarctic and 2010 in the Arctic. The signals measured from repetitive ramming under the heavy ice condition in 2012 in the Antarctic Ocean were classified into the five profiles. And the classified ice load signals were analyzed with a focus on raising time, half-decaying time and total time duration. Also, the signals measured from continuous icebreaking in 2010 in the Arctic Ocean were analyzed in the same way as the ramming data. Finally, the time histories of ice load signals were summarized from the viewpoint of speed change at the time of ice load, and two data sets were compared.

Topics: Stress , Ice , Ships , Signals
Commentary by Dr. Valentin Fuster
2018;():V008T07A006. doi:10.1115/OMAE2018-77850.

Model tests in ice are well-established to assess ice loads acting on ship-shaped structures. Model basins worldwide have elaborated different types of model ice over the past decades and gained confidence in e.g. predicting ship’s resistance which is validated by full scale data. Driven by industrial needs, the model ice was invented and modified with emphasis on the failure observed on ship hulls: Mostly flexural failure with only limited influence of crushing, i.e. against a vertical stem contour. Nowadays, the same model ice is occasionally used for structures exposed to ice action which are far from being ship-shaped, such as vertical sided monopiles or artificial islands. This approach is often questioned as the currently used model ice is usually insufficiently brittle, overstates out-of-plane deformation and flexural failure of the ice sheet, and transfers most of the ice load by a hard top layer rather than creating a wedge-shaped ice edge with a line-like contact approximately at middle height of the ice thickness as observed in full scale indentation tests. Therefore, results from tests with vertical structures in model ice have to be treated cautiously and not all observations are directly scalable. In an attempt to overcome the most severe issues with HSVA’s model ice in tests with vertically sided structures, a new way of initiating the formation of a model ice sheet was tested as a part of the IVOS project. Instead of spraying a top layer, the water in the basin was kept in motion by a wave maker while crystals formed. When the waves were stopped, an ice sheet with larger crystals in the top layer grew. A compliant vertical structure was pushed through this ice sheet and global and local loads were measured. The measurements were compared to tests with the same structure in conventional columnar model ice. Various ice properties were measured throughout the tests.

This paper introduces an alternative way to create a model ice sheet for tests with vertically sided structures utilizing a wavemaker, and discusses the findings from first model tests.

Topics: Ice
Commentary by Dr. Valentin Fuster

Polar and Arctic Sciences and Technology: Ice Management and Operations in Ice Evacuation in Ice

2018;():V008T07A007. doi:10.1115/OMAE2018-77397.

The Arctic plays a key role in the economic development of Russia. This region is fabulously rich with hydrocarbons and biological resources. One of the strategic goals in commercialization of the Arctic region is setting up of efficient transportation systems for year round navigation via the Northern Sea Route (NSR) to support shipment of various cargoes [1]. According to the latest studies, cargo vessels should be able to travel through NSR at speeds reaching 12 knots to make it a commercially competitively route. Highspeed moving can allow NSR to become competitive route as compared to the southbound route via Suez. It should be noted that ice conditions on this route are quite severe. Navigation in NSR of even ice-capable cargo carriers with icebreaker assistance will enable to increase the effectiveness of this shortcut shipping itinerary between Europe and the Pacific coast. For this purpose a novel nuclear Leader icebreaker has been designed, which, according to model tests in the Krylov Centre ice basin, will be able to sail in 2-meter continuous ice at 12 knots. The investigations of ship performance in ice at fast speeds are quite new and should be conducted very carefully. This paper focuses on some specific features of dynamic behaviour predicted for an icebreaker and a large-size vessel led by this icebreaker during speedy sailing in ice. It also discusses other important issues related to minimum power level requirement for vessels operating under these conditions as well as due account of the hydrodynamic resistance component in ice performance predictions.

Topics: Ice , Vessels , Icebreakers
Commentary by Dr. Valentin Fuster
2018;():V008T07A008. doi:10.1115/OMAE2018-77406.

From experience, OIRFP Prirazlomnaya (offshore ice-resistant fixed platform) installed in the Pechora Sea was seen to accumulate sustained piles of rubble ice in winter time. These features were formed along the platform walls and rested on the seabed (berm) obstructing operation of supply ships and crew evacuation. Researchers from the Krylov State Research Centre, St. Petersburg, were studying the ice piling processes and behavior under variation of environmental conditions (e.g., changes in ice drift headings) during design as well as service life of the platform. Moreover, the Krylov Centre ice basin was engaged in development of various ice management techniques to reduce the ice buildup as well as to remove rubble ice piles. The results of these investigations, which are presented in the paper, have led to a relatively simple solution for removing the rubble ice piles with a special-purpose shovel (excavator) mounted on the deck of a supply vessel. The paper describes details of the suggested solution and its implementation. The efficiency of this ice pileup management method has been proven in actual operating conditions.

Topics: Ice
Commentary by Dr. Valentin Fuster
2018;():V008T07A009. doi:10.1115/OMAE2018-78080.

The research investigates the influence of human expertise on the effectiveness of ice management operations. Ice management is defined as a systematic operation that enables a marine operation to proceed safely in the presence of sea ice. In this study, a method has been applied for assessing the effectiveness of ice management operations in terms of ability to modify the presence of pack ice around an offshore structure. This was accomplished in a real-time marine simulator environment as the venue for a systematic investigation. In the simulator, volunteer participants from a range of seafaring experience levels were tasked with individually completing ice management tasks. Recorded from 36 individuals’ simulations was the extent to which the ice in a defined area was impacted, measured in terms of tenths ice concentration. These responses were then compared to two independent variables: 1) experience level of the participant, categorized as either cadet or seafarer, and 2) ice severity, measured in ice concentration. The results showed a significant difference in ice management effectiveness between experience categories, where effectiveness was defined as the average drop in ice concentration during simulation. Results also showed that the human factor of experience and the environmental factor of ice concentration both had significant effects on average concentration drop. The research provides insight into the relative importance of vessel operator skills in contributing to effective ice management, as well as how this relative importance changes as ice conditions vary from mild to severe. This may have implications for training in the nautical sciences and could help to inform good practices in ice management.

Commentary by Dr. Valentin Fuster

Polar and Arctic Sciences and Technology: Numerical Ice Modeling Including Structure-Ice-Interactions

2018;():V008T07A010. doi:10.1115/OMAE2018-77253.

Based on cohesive element method (CEM), the continuous icebreaking process with different heel angles in level ice are simulated in this paper. The simulations are established in FEM software LS-DYNA and an icebreaking tanker - MT Uikku is assumed advancing with the certain heel angle in level ice. Firstly, the comparisons are made between the simulations and the model tests for the cases with zero heel angle. A good agreement is obtained between the simulated and measured data. Then the effects of different heel angles on ice resistance and ice breaking patterns are investigated and analyzed. The results show that ice resistance, average ice breaking length and average broken channel width present increasing trends with the increase of ship heel angle. The applied methods show a wide prospect to predict ice loads on marine structures in the level ice and simulate the ice-structure interaction process.

Commentary by Dr. Valentin Fuster
2018;():V008T07A011. doi:10.1115/OMAE2018-77260.

In order to simulate the movement of ice more accurately, this paper use overlapping grid methods combined with DFBI model to calculate the mutual interaction between an unconstrained ice cube and propeller, then the movement and force of the ice under the influence of propeller suction effect are analyzed. In the computational process, different working conditions are carried out by altering propeller rotation speed and ice-propeller radical distance. According to the computational results, when ice move near to the propeller disk, the force peak value in 3 directions will appear; and when the flow speed remain constant, the bigger of advance velocity coefficient, the higher probability of ice-propeller crashing.

Topics: Ice , Propellers
Commentary by Dr. Valentin Fuster
2018;():V008T07A012. doi:10.1115/OMAE2018-77283.

During the research of propeller-ice contact process, we found that shadowing effect has great influence on the ice loads of propeller blade. Therefore, more study in the shadowing effect would be helpful to solve the complicated propeller-ice contact problem. A numerical simulation model is established based on the coupling of peridynamics and panel method in this paper, and ice force for the whole blade and for blade back and blade face separately are obtained through the calculation of the simulation model. The influence law to ice loads of shadowing effect would be revealed clearly by comparing the loads of blade face with the loads of blade back .On this basis, more research is carried out on the mechanism of shadowing effect. In addition, a new calculation formula for shadowing coefficient is put forward in this paper. The results show that the influence of shadowing effect on propeller loads is well predicted by the calculation result of shadowing coefficient formula.

Topics: Ice , Milling , Propellers
Commentary by Dr. Valentin Fuster
2018;():V008T07A013. doi:10.1115/OMAE2018-77345.

In this study, we used multi-body dynamic (MBD) technique to numerically calculate the ice load of the icebreaker in pack ice conditions. Because MBD is a useful method for analyzing the dynamic behavior of a rigid body using the contact mechanism, MBD analyzes the interaction between each ice and icebreaker. Each ice and icebreaker also interact with the fluid. Simultaneously analyzing the interaction between fluids and float is difficult and complex, so Computational Fluid Dynamics (CFD) is used to simulate fluid-ice interaction and apply it to ice modeling. The simulation was performed in the time domain and compared to the average ice impact load obtained from experiments in an ice traction tank.

Commentary by Dr. Valentin Fuster
2018;():V008T07A014. doi:10.1115/OMAE2018-77808.

Sea ice forms in a dynamic environment that affects its morphology. This results in the inhomogeneity of ice reflected for example in its thickness variation, flaws in terms of brine channels or cracks, presence of snow cover, and its various deformed states undergoing freeze-thaw cycles. This sea ice inhomogeneity introduces important effects observable in the response of a structure when it is interacting with sea ice. Failure to account for the randomness introduced by the sea ice inhomogeneity would risk producing unrealistic simulations not seen in the actual world. In this paper the proposed approach to model randomness in numerical simulation of ice-induced vibrations is presented. This is achieved by accounting for randomness in the ice crushing force. The study is carried out using a purpose-developed numerical model that simulates the ice-induced vibrations of structures. The model adopts a phenomenological basis that aims to capture the important processes during the dynamic interaction between ice and the structure. Full-scale measurement data is used for comparison in this study.

Commentary by Dr. Valentin Fuster
2018;():V008T07A015. doi:10.1115/OMAE2018-77884.

Spectral methods such as Fourier Transform are used to analyze the response of structures to reveal characteristics of time series in frequency domain, as is typically done in the study of ice-induced vibrations. The limitations of these methods lie in that they assume the signal to be stationary and decompose the signal as a whole. Wavelet Transform has been developed for several decades to overcome these limitations. In this paper, the technique of Wavelet Transform is applied to ice force and structural response signals that provides a means to simultaneously analyze the data in both time and frequency domains. The results show that the applied method provides useful visualization of signals, allowing fast identification of vibration events of interest from long time series. A frequency locked-in event can be identified at intervals with high energy concentration at the fundamental frequency of the structure and relatively small variations in phase lag between the load and response. A random vibration is found that energy at the fundamental frequency of the structure occurs intermittently in time domain and almost all frequencies are excited showing a wide band spectrum. Simulation results obtained from a purpose-developed numerical model show that the same characteristics can be observed compared to full-scale measurements from the Norstromsgrund lighthouse.

Commentary by Dr. Valentin Fuster
2018;():V008T07A016. doi:10.1115/OMAE2018-77898.

The interaction between sea ice and sea water is a complicated fluid-solid coupling dynamic process during the operation of polar ships. Using the finite element numerical simulation software LS-DYNA to simulate the continuous ice breaking of icebreaker, the ice load numerical calculation method considering the ice water coupling is presented. The effect of ice water coupling on ice load is studied. Based on the ice pool test data and the calculated results of this paper, the accuracy and rationality of the algorithm are verified. On this basis, the multiple factors affecting the coupling between sea ice and sea water are further studied, including the thickness of sea ice and the collision velocity of ship and ice which are affected by the environment of different polar sea areas. By simulating the numerical results obtained from the collision ice breaking of the targeted ship, the influence of various factors on the coupling effect between sea ice and sea water is summarized, and the local strength of the hull head structure is checked and evaluated. Furthermore, the impact-type icebreaking ability of the hull is put forward, which has certain guiding significance for the development of ship ice collision numerical simulation.

Topics: Stress , Ice , Water
Commentary by Dr. Valentin Fuster
2018;():V008T07A017. doi:10.1115/OMAE2018-77991.

For the evaluation of ship performance in ice and ice loads on the ship hull, numerical simulation methods have been increasingly developed in recent years. In these models, the shapes of ice cusps broken from the intact ice sheet are idealized as either part of a circle or a triangle. Effects arising from the geometry of the loading area are neglected or idealized. Since the proper definition of the geometry of ice cusps is one of the key factors in numerical models, this paper introduces a new icebreaking pattern based on theoretical deviation. The finite difference method is adopted to approximate the deflection field of the wedge plate. This model takes a large set of factors as input while consuming little computation time. The outcome provides some new features compared to previous models. The results are validated using full-scale measurements of ice cusps around a ship hull, based on stereo camera recording and image processing. The validation shows that the derived method is appropriate in predicting realistic icebreaking patterns. Hence, it is plausible that its implementation in numerical models for ship performance in level ice will lead to improved prediction of the ship performance and ice loads on the hull.

Commentary by Dr. Valentin Fuster
2018;():V008T07A018. doi:10.1115/OMAE2018-78200.

The ice breaking capacity of the icebreaker depends on the geometric characteristics of the bow. Selecting reasonable bow configuration and characteristic parameters is helpful to improve the ice breaking capacity. In the ship parameters, the bow rake angle directly influences the ice breaking ability and the dipping efficiency. The ship collision with ice is simulated by using nonlinear dynamic analysis software LS-DYNA. By changing the bow rake angle, the collision force curves are obtained, and the ice breaking ability and efficiency of the polar ship with three bow configurations are calculated and compared with the ice resistance calculated by Riska formula. Through the analysis of the average longitudinal collision force and the ice breaking distance, the optimum bow configuration is selected. Combined with the calculation of the open water resistance, the scheme with the bow rake angle of 13 degrees is the best in the resistance performance.

Commentary by Dr. Valentin Fuster
2018;():V008T07A019. doi:10.1115/OMAE2018-78340.

Diminishing ice presence in the Arctic provides the potential for extended operable period for oil and gas exploration in the Arctic. Floaters are a flexible solution for such scenario whereas they can fully take advantage of the extended drilling season as well as operate in other harsh environment regions during the off-season. Such floaters can disconnect and reconnect to avoid large ice features such as icebergs and multi-year ice ridges. However, they still need to encounter relatively large level ice. Accompanying icebreakers will ideally assist in breaking the level ice into manageable pieces. The interaction of such level ice floes with floater has a significant influence on the dynamic ice load on the floater and resulting mooring load. There is significant uncertainty in the simulation of level ice-floater interaction numerically. Most of the current research focuses on the influence of ice breaking and subsequent flow of the broken ice around the floater. However, the hydrodynamic load due to the incoming level ice will also affect the response of the floater, which is usually not simulated. A recent study simulated the multibody hydrodynamics of level ice and floater Such multibody hydrodynamic analysis is computationally expensive, and complexity in the modelling is a hindrance to its implementation in the design phase. The present study, therefore, employs a conservative estimation to include the effect of wave load on the floater in addition to the ice load. Parametric studies are performed to estimate this effect by varying the incoming wave amplitude and wave period, ice sheet thickness, ice drift velocity, floater’s hull angle, mooring stiffness and the distance of large ice-sheet from the floater. Significant impacts of waves on the floater in terms of total force are observed which clearly reflects the importance of this study. The effect of mooring stiffness on total load is also investigated at the end of this study which can be considered as a foundation for further research on optimizing the mooring stiffness for such kind of arctic floater.

Topics: Stress , Waves , Ice
Commentary by Dr. Valentin Fuster
2018;():V008T07A020. doi:10.1115/OMAE2018-78592.

As offshore activities in the Arctic constitute a relatively new field with only a handful of relevant operations to draw experience from, and since full-scale trials are extremely expensive, there is an expressed need for much more extensive, detailed and cost-efficient analysis of concepts based on numerical simulations. However, until recently simulation tools of sufficient quality to perform such numerical analysis have not existed. The only verification available has been through a limited set of experiments in ice model basins. Today, this has changed, partly through the efforts at the Norwegian University of Science and Technology (NTNU) hosting SAMCoT (Centre for Research-based Innovation - Sustainable Arctic Marine and Coastal Technology), laying the foundation of a versatile and highly accurate high-fidelity numerical simulator for offshore structures in various ice conditions such as level ice, broken ice and ice ridges.

Arctic Integrated Solutions AS (ArcISo) is a spin-off company from NTNU established in 2016 with the vision of increasing the technology readiness level of SAMCoT’s numerical models to become a professional software package for the analysis of sea ice actions and action effects on Arctic offshore and coastal structures. This software package is called Simulator for Arctic Marine Structures (SAMS) and it was first released in 2017. This paper introduces the software implementation and the theoretical basis of SAMS, and it discusses the use of full-scale data to validate the simulator.

Commentary by Dr. Valentin Fuster
2018;():V008T07A021. doi:10.1115/OMAE2018-78765.

In this paper, we use 3D discrete element method (DEM) to simulate ship penetration through a non-cohesive rubble pile presenting a ridge keel. We study the effect of the pile width on the rubble resistance and the relation between the resistance records and rubble deformation. The peak rubble resistance increases with the rubble pile width, but the rate of the increase is not constant. The peak rubble resistance values from the simulations with the widest rubble piles are compared to the ones yielded by the analytical models with success.

Commentary by Dr. Valentin Fuster

Polar and Arctic Sciences and Technology: SKT Project

2018;():V008T07A022. doi:10.1115/OMAE2018-78552.

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with two anchor handling supply vessels; Magne Viking and Tor Viking. The data collection included monitoring of ice conditions and response of Magne Viking during ice interaction events. The present paper describes numerical simulations of broken ice and intact ice interaction events with single point moored Magne Viking.

Topics: Ice , Modeling
Commentary by Dr. Valentin Fuster
2018;():V008T07A023. doi:10.1115/OMAE2018-78553.

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with two anchor handling tug supply vessels. The vessels Tor Viking and Magne Viking were used as Support vessel and Moored vessel, respectively. This paper describes the above mentioned marine assets, mooring analysis, mooring configuration, mooring and unmooring procedures, including quick disconnection system design and operation.

Topics: Ice
Commentary by Dr. Valentin Fuster
2018;():V008T07A024. doi:10.1115/OMAE2018-78555.

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with the two AHTS (anchor handling tug supply) vessels, Magne Viking and Tor Viking. The main objective of the SKT project was to collect full scale data for calibration of numerical models. This paper describes the design and setup of the tailor-made data acquisition system, including description of the individual sensors in the system as well as how the data was handled during the different project phases. A description of how all data was recorded, time synced and stored is given. Data post-processing, storage and visualization done within the scope is also described.

Commentary by Dr. Valentin Fuster
2018;():V008T07A025. doi:10.1115/OMAE2018-78556.

Dynamic Positioning Systems are used in numerous types of marine operations. Due to the important differences in the external loads acting on the vessel, standard DP systems may fail to perform in ice conditions. Moreover, specific principles and position keeping philosophies should be applied in ice covered waters. The objective of the paper is to elaborate on these aspects by presenting and analyzing full scale DP tests. These tests were a part of the station-keeping trials performed in March 2017 in drifting ice in the Bay of Bothnia. Control algorithms limitations of Standard DP Systems are presented, showing the necessity of new control principles. The importance of crew training is also demonstrated along with the approaches to keep position in ice.

Commentary by Dr. Valentin Fuster
2018;():V008T07A026. doi:10.1115/OMAE2018-78579.

This paper introduces the concept of distributed motion sensing for stationkeeping vessels in ice infested waters. During the SKT 2017 project, conducted in February and March 2017 in the Bay of Bothnia, five inertial measurement units were installed on the vessel Magne Viking. Four of the sensor units were installed at different positions inside the hull of the vessel, which enabled the system to locally measure ice-induced vibrations in the hull of the vessel. The fifth sensor unit was installed at a central position of the vessel and served as reference sensor for measuring the acting global load on the vessel. Under stationkeeping the global load measured on the ship should be close to zero, because the environmental load is equal to the force from the stationkeeping system. However the remaining four motion sensor units in the hull also measured locally induced vibrations. The study shows that this sensor configuration allows for the detection of changes in the acting load against the vessel. This is demonstrated with motion data obtained during the stationkeeping trials on the vessel Magne Viking.

Topics: Stress , Ice , Vessels , Hull
Commentary by Dr. Valentin Fuster
2018;():V008T07A027. doi:10.1115/OMAE2018-78583.

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia. The anchor handling tug supply vessel Magne Viking, performed station keeping operations in various ice conditions, including managed and non-managed ice. Physical ice management was used to manage the approaching ice to a target condition suitable for the station keeping tests, and to enable other essential operations including deployment and retrieval of the mooring spread and other equipment. Given the objective of the trials, physical ice management activities were performed in such a way to allow investigation of various relevant parameters that influence the managed ice condition. Additional tests were also performed for the sole purpose to assist with validation of Aker Arctic’s ice management software “AIMS”, including tests designed to estimate the performance of the vessels under different ice conditions.

This paper focuses on the physical ice management operations performed by the ice management vessel Tor Viking (TV) during the Station Keeping Trials in ice (SKT). Also included is a discussion on how AIMS was used in the planning phase and how simulations compared with actual observations.

Topics: Ice
Commentary by Dr. Valentin Fuster
2018;():V008T07A028. doi:10.1115/OMAE2018-78587.

Station-keeping trials were undertaken in drifting ice in the Bay of Bothnia with two anchor handling supply vessels; Magne Viking and Tor Viking. This paper describes test scenarios which were performed with Magne Viking in moored, Dynamic Positioning and transit modes. An overview of the tests performed during the trials is presented, outlining the range of environmental and operational parameters. Examples of specific ice interaction scenarios are highlighted with illustrative measurement data providing observational insight into the performance and processes.

Topics: Ice
Commentary by Dr. Valentin Fuster
2018;():V008T07A029. doi:10.1115/OMAE2018-78588.

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with two anchor handling tug supply vessels, Magne Viking and Tor Viking. The primary objective of the Station-keeping Trials in Ice project (SKT) was to gather full-scale data on a stationary floating structure in ice. The data will be used for validation of numerical and physical models, that will in turn increase confidence in modelling tools for design and operation in ice-covered waters. The principal requirement of the project was to safely collect the maximum amount of data meeting the quality requirements within the available budget and timeframe. This paper presents the overall project planning and execution, while more details are provided in the companion papers.

Topics: Ice
Commentary by Dr. Valentin Fuster
2018;():V008T07A030. doi:10.1115/OMAE2018-78620.

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with the two anchor handling tug supply vessels Magne Viking and Tor Viking. During the trials observations of ice and metocean conditions were performed via a range of platforms and techniques. The purpose of the observations was to document the main physical parameters affecting the station-keeping vessel and ice management vessel, as well as giving tactical information on ice conditions and input to simultaneous numerical simulations. Measurements of meteorological parameters (wind speed, wind direction, air temperature, etc.) were done from the two vessels and supplemented with manual observations. Ice drift was independently measured by drifting ice trackers and ADCPs (also measuring ocean current) moored on the sea bed. Measurements of ice thickness were carried out with moored Ice Profiling Sensors (IPSs) and manual ice core samples, which were also analyzed for salinity and temperature profiles. The IPS ice thickness data was later processed together with the ice drift to provide 2D spatial data. The deepest ice ridge keels ranged from 5.4 m at the site with the most benign ice conditions to 10.9 m at the most severe site. Ridge frequency also increased from 2 ridges km−1 to 16 ridges km−1 at the most severe site (given a keel threshold of 3 m). In the present study, statistical summaries of the different time series collected at the sites of the station-keeping trials are presented, highlighting the variability in the ice conditions. Using the vessel tracks and overall drift of the broken channels, ice thickness and drift measurements are classified as being inside or outside the managed ice zone.

Topics: Ice
Commentary by Dr. Valentin Fuster
2018;():V008T07A031. doi:10.1115/OMAE2018-78709.

In connection with the Statoil SKT project, DNV GL have developed a method for estimating ice loads on the ship hull structure and mooring tension of the anchor handling tug supply (AHTS) vessel Magne Viking by full scale measurements. In March 2017, the vessel was equipped with an extensive measurement system as a preparation for the dedicated station-keeping trial in drifting ice in the Bay of Bothnia. Data of the ice impacts acting on the hull were collected over the days of testing together with several other parameters from the ship propulsion system. Whilst moored, the tension in the mooring chain was monitored via a load cell and logged simultaneously to the other parameters. This paper presents the processes involved in developing the measurement concept, including the actual installation and execution phases. The basic philosophy behind the system is described, including the methods used to design an effective measurement arrangement, and develop procedures for estimation of ice loads based on strain measurements. The actual installation and the process of obtaining the recorded data sets are also discussed.

Commentary by Dr. Valentin Fuster

Polar and Arctic Sciences and Technology: Structures in Ice

2018;():V008T07A032. doi:10.1115/OMAE2018-77111.

The University of Rostock has generated dimensioning equations to calculate the strength of twistlock systems under non-standard loading conditions on offshore platforms in the POLAR project in the last years. These dimensioning equations have been presented on previous OMAE conferences. In this paper ultimate strength analyses are conducted to assess the safety margin between elastic design and final rupture. The validation of the local system is shown and the results of the experiment and the simulation are analyzed and compared. In these experiments twistlock systems are subjected to cyclic loads, long-term tensile load at design level and ultimate loads. The experiments are conducted with a heavy duty hydraulic test rig. The results show agreement between experiment and simulation with regard to the rupture behavior and the force-displacement relationship.

Commentary by Dr. Valentin Fuster
2018;():V008T07A033. doi:10.1115/OMAE2018-77314.

Ice flexural strength is an important parameter in the assessment of ice loads on the hulls of ice-class ships, sloped offshore structures or sloped bridge piers. While scale effects are well known for compressive ice strength, there has been debate as to whether or not scale effects in ice flexural strength exist. To investigate scale effects during flexural failure of freshwater ice, a comprehensive up-to-date database of beam flexural strength measurements has been compiled. The data show a considerable decrease in flexural strength as the specimen size increases, when examined over a large range of scales. An empirical model of freshwater ice flexural strength as a function of beam volume has been developed using regression analysis.

Topics: Ice , Bending strength
Commentary by Dr. Valentin Fuster
2018;():V008T07A034. doi:10.1115/OMAE2018-78409.

52,000 deadweight ton class icebreaking tanker is designed to comply with Russia Maritime Register of Shipping(RMRS) ice category Arc7 and IACS CSR-H.

The ice breaking load was obtained from the DDePS of the ABS Classification Society and the limit load calculation was examined through the Abaqus nonlinear analysis.

The collision location and iceberg type selection were adopted to define iceberg-hull collision scenarios. Nonlinear analysis simulated ice breaking process by using LS-DYNA.

Commentary by Dr. Valentin Fuster
2018;():V008T07A035. doi:10.1115/OMAE2018-78593.

The Simulator for Arctic Marine Structures (SAMS) has emerged on the foundation of a number of scientific models developed at SAMCoT – Centre for Research-based Innovation - Sustainable Arctic Marine and Coastal Technology hosted by NTNU – as a versatile numerical tool for the analysis of sea ice actions and action effects on Arctic offshore structures. The current capabilities of SAMS allow engineers to analyse icefloe impacts and ice loads on arbitrary marine structures in various environmental conditions; simulations may involve both fixed and floating structures, non-rigid multi floe interactions, ice breaking and ice rubbling, wind, current and propeller-flow effects on both structures and ice. All these capabilities can be combined to model also complex marine operations in the Arctic and subarctic regions.

As SAMS can be applied in both full- and model scales, a number of available experimental case studies from the field and ice tanks can be reanalysed with the new simulator to ensure the high fidelity of the simulations and to establish a validation basis. This paper presents several of such case studies and discusses further validation possibilities.

Commentary by Dr. Valentin Fuster

Polar and Arctic Sciences and Technology: Vessels in Ice Including Maneuvering

2018;():V008T07A036. doi:10.1115/OMAE2018-77404.

Ice management (IM) is often required to support offshore production of oil and gas in freezing seas. It helps to mitigate ice impact on marine structures and thus minimize risks of accidents as well as to increase weather windows for marine operations. One of the IM tactics is to use an icebreaker for producing a zone of managed ice for ensuring safe and efficient operation of marine facilities: platforms, offloading terminals, tankers, etc. The choice of the right icebreaker which is best capable to cope with the IM jobs is quite a challenging task. This paper suggests an approach to objectively compare operational efficiency of different icebreakers in performance of some typical IM tasks. This approach made it possible to work out universal criteria for assessing the efficiency of these ships. The criteria of icebreaker efficiency and operational performance have been derived from actual ice breaking and maneuvering data including safety aspects of required icebreaker maneuvers. The paper contains case studies with estimation of the said criteria for a number of IM icebreakers expected to be used for ice management in the south-eastern part of the Barents Sea.

Topics: Safety , Ice , Icebreakers
Commentary by Dr. Valentin Fuster
2018;():V008T07A037. doi:10.1115/OMAE2018-77464.

The Arctic ocean has been the focus of increasing activities in oil and gas, marine traffic and fisheries as the resources in the Arctic area becomes more attractive for exploitation. There have been several studies on the response of ships and structures in ice covered waters, mainly for oil and gas applications. This paper presents a scenario simulation model for fisheries, crab pot retrieval, in partially ice covered waters. Snow crab fisheries in the Barents Sea is an ongoing commercial activity where partial ice covers may drift over crab pots which need retrieval. This scenario is unique in the sense that the ship and ice can be expected to experience wave forcing in addition to the ice–structure interaction. The complexity of such scenarios favor simplified models and a coupled simulation model consisting of ship hydrodynamics, ice hydrodynamics, ice–ice and ice–ship interactions. A case vessel is presented together with a scenario simulation model which is used to assess the ice impact forces during operations and the amount of ice interaction which can be expected in the region where the pot string is retrieved from the ocean.

Topics: Ice , Vessels , Water
Commentary by Dr. Valentin Fuster
2018;():V008T07A038. doi:10.1115/OMAE2018-77668.

With increasing need to utilize inland waterways (IWW), the design for IWW vessels gains attention both from a transport efficiency and an emission control point of view. The primarily issue is to estimate the ice pressure acting on the ship hull for inland waterways. Ice information for Lake Mälaren is extracted and analysed in this work. Since the ice properties have great influence on the impact load, they are studied based on empirical formulae and are calibrated by reference data. The ice impact is then predicted for an inland water barge. Probabilistic method is selected to derive the load based on available field test data. Several parent datasets are chosen, and different design strategies are implemented to evaluate the ice impact load and investigate the influences from exposure factors. The paper finds that the design curve of α = 0.265a−0.57 can be used for Lake Mälaren. The approach itself introduces a possible way to investigate loads on ice affected IWW.

Topics: Pressure , Ice , Vessels
Commentary by Dr. Valentin Fuster

Petroleum Technology: Drilling Geomechanics

2018;():V008T11A001. doi:10.1115/OMAE2018-77851.

Solids/sand production is an unintended byproduct of the hydrocarbon production that, from an operational point of view, might potentially lead to undesirable consequences. This paper focuses on a study centered in the geomechanical perspective for solids production. An integrated workflow is presented to analyze the combined effect of reservoir pore-pressure, drawdown, in-situ stress, rock properties and well/perforations orientation on the onset of solid production. This workflow incorporates analyses at multiple scales: rock constitutive modeling at lab scale, 1D geomechanical models at wellbore scale along well trajectories, a 3D geomechanical model at the reservoir scale and 3D/4D high resolution reservoir - geomechanical coupled models at the well and perforation scale.

1D geomechanical models were built using log and field data, drilling experience and laboratory tests in order to characterize in situ stresses, pore pressure and rock mechanics properties (stiffness and strength) profiles for several wells. Rock shear failure mechanism was also analyzed in order to build a pre-drill model and evaluate the wellbore stability from a geomechanical point of view.

Pre-production stress modeling was simulated to obtain a representative initial stress state integrating 1D geomechanics well results, 3D dynamic model and seismic interpretations. Mechanical properties were distributed considering properties calculated in the 1D geomechanical models as input. 3D stress field was validated with in-situ stress profiles from 1D modeling results. This simulated pre-production stress state was then used as an initial condition for the reservoir - geomechanical coupled simulations. Effective stress changes and deformations associated to pore pressure changes were calculated including the coupling between reservoir and geomechanical modeling.

Finally, a 3D/4D high resolution well scale reservoir - geomechanical coupled numerical model was built in order to determine the threshold of sand production. A limit of plastic strain was obtained based on numerical simulations of available production data, DST and ATWC tests. This critical plastic strain limit was used as a criterion (strain-based) for rock failure to define the onset of sand production as a function of pore pressure, perforation orientation and rock strength. Conclusions regarding the perforation orientations related to the possibility of producing solids can support operational decisions in order to avoid undesirable solid production and therefore optimize the production facilities capacity and design to handle large amounts of solids and/or the clogging of the well.

Commentary by Dr. Valentin Fuster
2018;():V008T11A002. doi:10.1115/OMAE2018-77928.

Several wellbore instability problems have been encountered during drilling a shale formation in an offshore field, leading to the collapse of the main borehole and resulting in several sidetracks. In this study, an integrated 1D & 3D Geomechanical model was built for the field in order to investigate the major factors that control the instability problems from a Geomechanical point of view and to design an optimum mud window for planned wells in the field. Effect of bedding on wellbore stability was the most important factor to explain the observed drilling events.

Optimized well paths for planned wells were proposed based on results of a sensitivity analysis of the effect of bedding orientation on wellbore stability. It has been observed that bedding exposed depends not only on well inclination but also on dip of the formation, attack angle, and azimuth.

Commentary by Dr. Valentin Fuster
2018;():V008T11A003. doi:10.1115/OMAE2018-77936.

In this study an extensive experimental program has been carried out in order to characterize the mechanical behavior of two weak sandstone formations of an offshore field for application to sand production modeling. The experimental tests included Scratch tests, Triaxial tests and Advanced thick wall cylinder tests (ATWC) where the sand production initiation and the cumulative sand produced were registered.

Numerical simulations of experimental tests were then performed using an advanced elasto-plastic constitutive model. Triaxial tests simulations allowed calibrating the constitutive model parameters. These parameters were employed for the numerical simulation of the ATWC in order to determine the equivalent plastic strain threshold required to the onset of sand production observed in laboratory for sanding assessment.

Results obtained highlight the importance to use a realistic representation of the rock behavior focusing on post-yield behavior in order to build confidence in model predictions.

Commentary by Dr. Valentin Fuster
2018;():V008T11A004. doi:10.1115/OMAE2018-78152.

Predicting drilling risks in advance is a major challenge in areas that lack drilling experience, and even when information from offset wells is available. Large overpressure was found at TD of an offshore exploratory well drilled mainly through shale. None of the other two previously drilled offset wells in the area had shown any sign of such a high overpressure. This study presents two complementary approaches to gain insight on the overpressure generation mechanisms. The effect of chemical compaction is first evaluated in terms of well cuttings analysis, including sample washing, high-resolution photo catalog, automated mineralogy and X-ray diffraction clay mineralogy analysis. The obtained mineralogical results confirm the presence of the dehydration diagenetic process involving the transformation of smectite to illite. Consequently, a numerical model is presented which combines the effect of mechanical and chemical compaction to predict pore pressure values very close to the overpressure observed during drilling. The model reproduces the depositional history of the lithological column by coupling mechanical and chemical compaction with fluid flow over geological time, and it allows predicting stress, porosity and pore pressure evolution at different geological ages. Calibration and verification of the results of the pore pressure model is done by comparison to drilling experience and logs (post-drill pore pressure profile, geology tops and density/porosity logs).

Commentary by Dr. Valentin Fuster

Petroleum Technology: Drilling Mechanics

2018;():V008T11A005. doi:10.1115/OMAE2018-77202.

The drill string used in drilling oil and gas wells is a long and slender structure that is confined by the wellbore wall and subject to significant axial, lateral and torsional vibrations while drilling. Detection and mitigation of drill string vibrations are especially important, as vibrations can be hard to detect at the surface, yet cause significant damage to the drill bit, downhole tools and the formation being drilled.

Study of the drilling process by downscaling to laboratory conditions is an attractive prospect as it is a cost-efficient alternative to dedicated large-scale testing and it can be instrumented to provide vibration measurements from different locations along the string. However, the extreme geometrical length scales, the complex wellbore trajectories and the large mechanical strains on the drill string lead to challenges when attempting to downscale the drilling process to manageable laboratory conditions.

Downscaling based on similarity analysis provides consistent scaling laws for predicting large-scale dynamics based on observations from the downscaled test drilling rig. We perform a similarity analysis for an example full scale drill string that illustrates these challenges in terms of similarity criteria for an equivalent laboratory model of the drill string. We focus particularly on the geometric and mechanical properties of the drill string and consequences of downscaling on the time scale and the forces in the string. We illustrate the downscaling criteria through numerical simulations by solving the governing equations of motion at different scales, and provide recommendations for downscaling based on widely available material types.

Commentary by Dr. Valentin Fuster
2018;():V008T11A006. doi:10.1115/OMAE2018-77882.

The scientific drillship Chikyu, operated by JAMSTEC has faced the problems with drill pipe damage and failure. After a failure, we examined the surface-measured drilling data, including Fourier transform analysis and spectrogram, and conducted an outlier investigation with an autoregressive model. We found some possible indications of top drive torque anomalies among the surface-measured drilling data. The purpose of this study is to attempt anomaly detection of top drive torque by applying machine learning approaches to such pre-examinations.

Data acquired during the drilling operations of the Chikyu are first analyzed to observe the operations and determine the characteristics of the drilling data. Several hundred sets of surface drilling data are extracted and prepared as labeled learning data. Machine learning is then performed using several algorithms to build predictive models for anomaly detection of top drive torque. Simulations using these predictive models are then conducted for other sets of drilling data, including the anomaly conditions acquired during the operations of the Chikyu. The results demonstrate the validity of the predictive models.

This study applies machine learning technique to the anomaly detection of the top drive torque with aim of preventing the drill pipe damage and failure. This paper describes our approaches in detail and discuss the results.

Commentary by Dr. Valentin Fuster
2018;():V008T11A007. doi:10.1115/OMAE2018-78229.

Offshore drilling with drill string over 10,000m long has many technical challenges. Among them, the challenge to control the weight on bit (WOB) between a certain range is inevitable for the integrity of drill pipes and the efficiency of the drilling operation. Since WOB cannot be monitored directly during drilling, the tension at the top of the drill string is used as an indicator of the WOB. However, WOB and the surface measured tension are known to show different features. The deviation among the two is due to the dynamic longitudinal behavior of the drill string, which becomes stronger as the drill string gets longer and more elastic. One feature of the difference is related to the occurrence of high-frequency oscillation.

We have analyzed the longitudinal behavior of drill string with lumped-mass model and captured the descriptive behavior of such phenomena. However, such physics-based models are not sufficient for real-time operation. There are many unknown parameters that need to be tuned to fit the actual operating conditions. In addition, the huge and complex drilling system will have non-linear behavior, especially near the drilling annulus. These features will only be captured in the data obtained during operation.

The proposed hybrid model is a combination of physics-based models and data-driven models. The basic idea is to utilize data-driven techniques to integrate the obtained data during operation into the physics-based model. There are many options on how far we integrate the data-driven techniques to the physics-based model. For example, we have been successful in estimating the WOB from the surface measured tension and the displacement of the drill string top with only recurrent neural networks (RNNs), provided we have enough data of WOB. Lack of WOB measurement cannot be avoided, so the amount of data needs to be increased by utilizing results from physics-based numerical models. The aim of the research is to find a good combination of the two models. In this paper, we will discuss several hybrid model configurations and its performance.

Commentary by Dr. Valentin Fuster
2018;():V008T11A008. doi:10.1115/OMAE2018-78694.

To maintain high rate of penetration (ROP) and to realize automatic drilling, it is necessary to monitor and control the weight on bit (WOB). Generally, the WOB is measured at the wellhead, and it is called surface WOB (SWOB). During directional drilling, there is big difference between the SWOB and downhole WOB (DWOB). In this paper, an analytical model for torque and drag of the drillstring is developed to calculate the DWOB. When building the model, the well profiles are separated to two categories, including straight section and curved section. Moreover, for the curved section, the azimuth and inclination of a well are considered while modeling, adequately. Based on a set of field tests, the friction factors and DWOB are calculated. The results indicate that there is a good match in value and trend between the data calculated and the one measured. In practice, the model can be used to predict and adjust the DWOB in autodriller system for real-time drilling monitoring. In addition, the model can also be applied to estimate downhole conditions and diagnose drilling status.

Commentary by Dr. Valentin Fuster

Petroleum Technology: General Petroleum Technology

2018;():V008T11A009. doi:10.1115/OMAE2018-77190.

Multiphase flow is an important the phenomenon existing widely in nature, daily life, as well as petroleum and chemical engineering industry. It is especially important to understand the flow behavior of multiphase flow in a subsea hilly terrain and offshore pipelines. Accurate flow regime identification in multiphase flow is critical since multiphase flow affects the measurement accuracy of phase fraction, flow rate and other phase parameters.

The main objective of this research work is to obtain a better understanding of the multiphase flow characteristics in a long pipeline. In this study, the results of an experimental research on multiphase flow that investigates fluid characteristics in a pipe has been presented. The experimental unit consists of pipes that are made up of clear PVC, which is capable of producing several different flow regimes (Stratified, bubble, slug, and annular-mist flow) of gas-liquid flows. The entire length of the flow loop is 20.574 m. The experimental unit includes sensors such as pressure transducers, thermocouples and flowmeters that enable to measure the pressure ranges from 20–300KPa, temperature ranges from 0 to 20 °C and volume flow ranges from 12–45 liter/min at numerous locations respectively. In this experimental work, bubble, and slug flow regimes have been selected in the multiphase flow pattern to be examined on the multiphase flow assurance. The results of this research will provide valuable new experimental data on multiphase flow characteristics for designated flow regimes that can improve flow assurance in subsea conditions by including the temperature and Pressure effects.

Commentary by Dr. Valentin Fuster
2018;():V008T11A010. doi:10.1115/OMAE2018-77510.

Drilling industry operations heavily depend on digital information. Data analysis is a process of acquiring, transforming, interpreting, modelling, displaying and storing data with an aim of extracting useful information, so that the decision-making, actions executing, events detecting and incident managing of a system can be handled in an efficient and certain manner. This paper aims to provide an approach to understand, cleanse, improve and interpret the post-well or realtime data to preserve or enhance data features, like accuracy, consistency, reliability and validity.

Data quality management is a process with three major phases. Phase I is an evaluation of pre-data quality to identify data issues such as missing or incomplete data, non-standard or invalid data and redundant data etc. Phase II is an implementation of different data quality managing practices such as filtering, data assimilation, and data reconciliation to improve data accuracy and discover useful information. The third and final phase is a post-data quality evaluation, which is conducted to assure data quality and enhance the system performance. In this study, a laboratory-scale drilling rig with a control system capable of drilling is utilized for data acquisition and quality improvement. Safe and efficient performance of such control system heavily relies on quality of the data obtained while drilling and its sufficient availability. Pump pressure, top-drive rotational speed, weight on bit, drill string torque and bit depth are available measurements.

The data analysis is challenged by issues such as corruption of data due to noises, time delays, missing or incomplete data and external disturbances. In order to solve such issues, different data quality improvement practices are applied for the testing. These techniques help the intelligent system to achieve better decision-making and quicker fault detection. The study from the laboratory-scale drilling rig clearly demonstrates the need for a proper data quality management process and clear understanding of signal processing methods to carry out an intelligent digitalization in oil and gas industry.

Commentary by Dr. Valentin Fuster
2018;():V008T11A011. doi:10.1115/OMAE2018-77722.

Global warming is considered the most challenging issue facing humanity today, with many research studies now focusing on investigating the main cause of this problem. Studying the behaviour of carbon dioxide in its different phases can provide the key to resolving this critical issue. In the present study, pipe flows are used to investigate the behavior flow of water-CO2 mixtures at different pressures and temperatures. The flow rate and pressure of water and CO2 are changed by using a pump placed before the mixing point. Pressure and temperature levels are recorded by sensors and thermocouples affixed at points along the pipe loop. The flow rate of water and carbon dioxide is changed simultaneously, and the flow regime of two-phase water-CO2 flow is visualized through transparent tubes. After repeating experiments several times, we found that the mean pressure drop along the tube for water-CO2 system flow is about 4 kPa/m. We also predict that the flow regime of the flow is often intermittent.

Commentary by Dr. Valentin Fuster
2018;():V008T11A012. doi:10.1115/OMAE2018-77996.

The transport of Non-Newtonian fluids through pipelines and mud circulation in wellbores often occur in turbulent flow regimes. In this study, experiments and computational fluid dynamics (CFD) models are used to examine the influence of yield power law (YPL) fluid rheological properties on pressure loss in the flow loop in turbulent flow. Three Non-Newtonian fluids at different concentrations of Xanthan gum solutions (0.05%, 0.10% and 0.15%, by weight) are studied at flow rates ranging between 400 and 800 L/min. A fully instrumented flow loop system was used, consisting of three main sections of different inclinations: 5 m long horizontal, 5 m vertical, and 3 m inclined 45° test section. Additionally, CFD codes of ANSYS CFX 17.2 are examined and compared to experimental results. These models are based on the Reynolds Averaged Navier-Stokes (RANS) equations. The comparison is done with the results of these investigations, based on vertical and horizontal pipe frictional pressure drops. The results show that the gap between experimental and CFD models has been increased in comparison with increase concentration Xanthan gum solution at the same density of fluids. Specifically, pressure loss rises with rises in the consistency index, k and flow behaviour index, However, rises in yield stress τ0 showed less impacts on frictional pressure losses. Given these simulation outcomes, it is clear that pressure drop in the Non-Newtonian fluid in one phase flow can be more accurately predicted by used the Reynolds-Stress Models (RSM) more than Eddy-viscosity models.

Commentary by Dr. Valentin Fuster
2018;():V008T11A013. doi:10.1115/OMAE2018-78001.

Reliability of blowout preventers (BOP) is central for the safety of both rig workers and the surrounding environment. Analysis of dynamic fluid conditions within the wellbore and BOP can provide quantitative data related to this reliability. In cases of a hard shut in, it is suspected that the sudden closure of rams can cause a water hammer effect, creating pressure vibrations within the wellbore. Additionally, as the blowout preventer reaches a fully closed state, fluid velocity can drastically increase. This results in increased erosion rates within the blowout preventer. To investigate fluid movement and pressure vibrations during a well shut-in, CFD simulations will be conducted. Dynamic meshing techniques within ANSYS® FLUENT can be utilized to simulate closing blowout preventer configurations for both 2-D and 3-D geometries. These simulations would deliver information that could lead to a better understanding of certain performance issues during well shut-ins. Such information includes flow velocity magnitude within the BOP and maximum pressure pulse values within the wellbore.

Commentary by Dr. Valentin Fuster
2018;():V008T11A014. doi:10.1115/OMAE2018-78057.

The objective of this work is to evaluate the influence of the implementing the downhole Passive Vibration Assisting Rotary Drilling (pVARD) Tool on enhancing drilling performance using a numerical study utilizing a Particle Flow Code (PFC-2D). The work is comprised of a numerical study of a simulation using the PFC-2D on an experimental work described in ARMA 15-492 (Rana et al, 2015). The numerical study was performed to validate the experimental work following the steps, procedure, and conditions performed in the laboratory work.

The numerical study of the laboratory work involves not only the evaluation of drilling rate of penetration (ROP), but it also includes the Depth of Cut (DOC) of the bit cutters and the Mechanical Specific Energy (MSE). This numerical work also includes comparison study of drilling performance under various configurations of the pVARD tool, which represents a controlled downhole vibration against the rigid drilling configuration that represents the conventional rotary drilling. The pVARD configurations involves pVARD low spring compliance, medium spring compliance, and high spring compliance. The drilling output parameters of DOC, MSE, and ROP are then studied and analyzed in all pVARD and non-pVARD configurations.

Likewise of the experimental work, the result of the numerical simulation approves the experimental work and it indicates the positive effect of utilizing the downhole pVARD on improving ROP. The drilling performance enhancement is also supported by the DOC and the MSE result.

Topics: Drilling , Vibration
Commentary by Dr. Valentin Fuster
2018;():V008T11A015. doi:10.1115/OMAE2018-78064.

Oil exploration in arctic regions is a very complex activity taking place in a sensitive environment, highlighted by social, wildlife and extreme weather conditions restricting operations to a very limited time window based on the opening of the Tundra season regulations which assesse the quality of the ice and snow coverage over frozen tundra, lakes and seas.

Thanks to new technologies, oil exploration in the arctic environment takes a great steps in 3D seismic acquisition methods passing from cable recording equipment and the dependence of sensor connectivity to a recording center and replacing this system with a very versatile system of wireless receivers units equipped with GPS positioning and time stamp recording and storing the seismic data “in situ”.

This new technology has allowed a high unit count of light receivers to operate in extreme conditions, which in the past was practically impossible given the limitations of the logistical support to carry out this type of operations in remote and difficult access areas. Definitely this technological development has allowed Repsol to explore a larger surface area in a single winter season acquiring high resolution seismic data that allows obtaining high quality images with better geophysical attributes.

Seismic sources have also undergone a notable evolution through the use of high productivity techniques of vibrating trucks moving from a set of multiple vibrators to a single vibrator emission getting up to date simultaneous source acquisitions which allows recording more information without waiting for a second set of vibrators or single vibroseis truck to start shaking to emit energy to the ground. The ability to vibrate at the same time with many sets of single vibrators allows operation on frozen sea either with grounded ice or vibrating on floating ice expanding the exploration boundary to the open sea zones.

The new technology has made it possible for Repsol to improve the operational capability of the crew without increasing the number of people or increasing the logistical support required to operate in remote and difficult access areas. This technological advance has allowed the improvement of the quality of oil exploration using 3D seismic techniques reducing the price per recorded trace or per surface source, increasing the possibility to acquire larger surfaces and better seismic data in a single winter season window. More importantly, these technologies have allowed affordable oil exploration with a high respect for the communities, the wildlife and the environment.

Commentary by Dr. Valentin Fuster
2018;():V008T11A016. doi:10.1115/OMAE2018-78101.

This study focuses on numerical simulation and evaluation of a hydraulically powered downhole Thruster. This device is numerically simulated and evaluated using ANSYS Fluent 17.2 to show its generation of pressure pulses that can induce downhole forces that magnify the downhole dynamic weight on bit (DWOB) using drilling mud. Such magnification of the DWOB can produce axial motion of the Thruster. Such axial motions, as proved by many publications can improve the drilling rate of penetration (ROP), release stuck pipes, and reduce frictions in non-vertical wells. The special inner design of the Thruster creates pressure pulses that can provide load impact on the drill bit leading to the increase of WOB that can enhance the drilling performance. The current stage of the study of the Thruster involves a mechanical design of the Thruster by the SolidWorks and an evaluation of the tool function and performance through pressure effect simulation by ANSYS Fluent 17.2. Initially, water is used as the fluid and the main parameters involved in the analysis are pressure and velocity. However, power-law as a non-Newtonian fluid is also used for comparison study in the section of pressure drop analysis.

The results are analyzed based on velocity pressure profiles, pressure drops, pressure effects with applications of various back pressures at several planes using water and power-law fluids.

Commentary by Dr. Valentin Fuster
2018;():V008T11A017. doi:10.1115/OMAE2018-78172.

3D seismic acquisition for Petroleum Exploration in the Artic Region is typically restricted to four operational months during the winter season. The area of the survey and the acquisition parameters need to be optimized and constrained to match the narrow time frame. Seismic operations must follow environmental regulations to avoid adverse impacts to the wildlife and sensitive terrains, including lakes, rivers, abandoned meanders, and the flora able to grow in the region. No vehicles or seismic equipment is allowed to operate above them in winter regardless of their protection by the snow cover. Furthermore, only vehicles and machinery are allowed to work on the frozen tundra or over frozen lakes and rivers with grounded ice. However, the ice thickness in the frozen lakes and rivers is not capable of supporting the heavy seismic vibrator. Therefore, many source points must be relocated which finally results in irregular source point distribution over the survey acquisition area.

The conventional method to recover source points around obstructions causes a concentrated redistribution of source points in the vicinity around the obstructions. An alternative operational method to recover source positions is presented in this paper. We used different types of geophysical analysis to evaluate the proposed optimized method for source recovery including traditional geophysical attribute analysis, illumination studies and attribute analysis of seismic data acquired in the Horse Shoe 3D project.

The proposed method can be implemented in areas with significant surface obstructions, either due to environmental restrictions, population, industrial or oilfield areas, or natural obstructions, etc.

An important conclusion is that the improvement in S/N and attributes obtained by the implementation of the proposed method for source recovery did require only a marginal increase in the work volume or resources for the project and so the cost and time of execution were not affected.

Commentary by Dr. Valentin Fuster
2018;():V008T11A018. doi:10.1115/OMAE2018-78217.

Mantle drilling, in which the oceanic crust is penetrated across the Moho to retrieve mantle samples, is one of the most challenging scientific projects of this century. This paper presents a literature survey on the development of mantle drilling, provides a brief introduction to mantle drilling, and introduces three drilling site candidates. Obstacles to mantle drilling are then presented, along with current R&D activities, plans, and considerations for solving those problems. For the purposes of this paper, significant contributions in mantle drilling research have been classified into the following categories: ultra-deep water, deep penetration, hard rocks, and high temperature. Necessary future research directions for mantle drilling are also described.

Topics: Drilling
Commentary by Dr. Valentin Fuster
2018;():V008T11A019. doi:10.1115/OMAE2018-78629.

The Arctic areas of Norway has brought many new challenges. In addition to harsh weather, drilling conditions are different.

The Barents Sea is different geologically compared to the North Sea area. A considerable amount of erosion bring older rocks higher up. It is observed that leak-off tests measured in Barents Sea wells shows abnormally high values. This is interpreted as a high stress state.

The paper analyze the stresses around a number of wells and conclude that it is very likely that a reverse fault stress state exists in these areas of the Barents Sea. This can bring positive effects because such a stress state may constrain induced fractures to propagate in a horizontal plane rather than towards surface, reducing the risk for reservoir leaks to surface. Also, a high compressive state may lead to more sealed faults, indicating a higher possibility for oil in place.

The paper will present the stress model and compare Barent Sea area to the North Sea. It will also show implications for wellbore stability, leaks from reservoirs and effects on sealing of major faults. Of particular interest is that leak potential from the reservoir is reduced in the Barent Sea as compared to other Norwegian oil fields. This may encourage more development in the Arctic areas.

Topics: Arctic region
Commentary by Dr. Valentin Fuster
2018;():V008T11A020. doi:10.1115/OMAE2018-78723.

This present study indicates experimental investigation about the impact of CO2 flooding on oil recovery and rock’s properties alteration in carbonate reservoir under the miscible condition. In order to compare the effect to initial pore characteristic, two type of carbonate rock was used; an Edward white represents homogeneous mainly consisted micropore, whereas an Indiana limestone represented heterogeneous mainly consisted macropore in this study. Under the miscible condition (9.65 MPa and 40°C), five pore volume of CO2 were injected into oil-wet carbonate rock, which was fully saturated with oil and connate water. After CO2 flooding, several analyses for each sample conducted to investigate oil recovery and rock properties change in porosity, permeability, and pore structure by chemical and physical reaction between CO2, water, and carbonate mineral before and after CO2 flooding by using core analysis, MICP, SEM, ICP, and X-ray CT techniques. From the results of oil recovery, it was more effective and larger in Edward white than in Indiana limestone. Because homogeneous characteristic with a large ratio of low permeable micropore in Edward white contributed to occur long reaction time between oil and CO2 for enough miscibility as well as to displace stably oil by CO2. Conversely, heterogeneous pore structure mainly consisted of high permeable conduit (macropore) in Indiana limestone has brought ineffective and low oil production. From the analysis of rock’s properties alteration, we found that, for the homogeneous sample, dissolution dominantly changed pore structure and became better flow path by improving permeability and reducing tortuosity. While plugging by precipitation of mineral particles was not critically affected rock’ properties, despite the sample mainly consisted small pores. In the case of the heterogeneous sample, both dissolution and precipitation critically affected change of rock’s properties and pore structure. In particular, superior precipitation in complex pore network seriously damaged flow path and change of rock’s properties. The largest porosity change markedly appeared in inlet section because of exposing rock surface from fresh CO2 during a long time. In conclusion, it shows that CO2 miscible flooding in carbonate reservoirs significantly affected to alteration of rock’s properties such as porosity, permeability, tortuosity, and pore connectivity, in particular in heterogeneous system compared with in homogeneous system. These experimental results can be useful to characterize carbonate rock as well as to study rock properties alteration on CO2 EOR and CCS processes.

Commentary by Dr. Valentin Fuster

Petroleum Technology: Human Factors in Oil and Gas Operations

2018;():V008T11A021. doi:10.1115/OMAE2018-78275.

The recent Macondo tragedy changed the health and safety landscape throughout the petroleum industry. Through such incidents, oil well cementing operations have gained widespread attention. Detailed technical reports of the Macondo well control incident outline the significance of the competent and efficient cementing operations.

The voluntary API RP 75 standard was recently modified into the current mandatory offshore Safety and Environmental Management Systems (SEMS II) regulations. The regulatory guidelines in the United States, dormant over the past 20 years, are finally being updated to meet current industry and public expectations. The human factor, overlooked for decades in the petroleum industry, serves as the catalyst behind the newly adopted offshore regulations.

This paper provides a brief overview of well integrity, and the pivotal role of cementing operations in well control. The critical role of human and organizational factors in cementing operations and well control is addressed. Furthermore. an outline of the newly implemented SEMS II regulations is also offered, with insight into adjustments that could enhance this program’s modest requirements.

Commentary by Dr. Valentin Fuster
2018;():V008T11A022. doi:10.1115/OMAE2018-78431.

The role of Human Factors, in complex environments like the oil and gas industry, has seen a paradigm shift over a very short span of time recently. Past studies have limited focus on the human system interfacial approach. However, the repeated failures have forced the industry and academia to take a closer look at the cascading failures with human errors perspective and conduct the root-cause analysis from the cognitive aspect. Traditionally, the knowledge, expertize, and competence took the driving seat while the human factors had been on the back burner. Lack of emphasis on Human Factors in academic research could be another reason for this laxity. Consideration of human factors in the design of systems is centered on the end user. Systems are designed to fit the physiological limitations of the people tasked with managing them. The design includes features that improve comfort and productivity, minimize errors, and minimize training time.

In this paper, first a review of crucial human factors in different well cycles such as drilling, well completion, fracturing, and abandonment will be presented. Through various cases studies, it will be shown that potential challenges can be mitigated with proper implementation of various elements for human factors such as situational awareness, team working, stress management and other non-technical skills. In addition, this paper reviews the critical components and perceived gaps of existing safety management systems in use as well as those elements that would be of most value to drilling taken from other sectors or industries on a ‘first principles’ basis. The paper attempts to highlight ’the myths, misconceptions, and realities of complex well operations’ that either deter changes or demand a new approach. It is the authors premise that if either a ‘clean sheet’ approach or more ‘actual cost’ weight was given to both common problems and low probability high consequence events such as kicks or loss of well control.

Commentary by Dr. Valentin Fuster
2018;():V008T11A023. doi:10.1115/OMAE2018-78557.

Drilling operations involve significant heat transfer between the drilling mud, downhole tubulars, and surrounding formation. Such heat transfer causes changes in drilling fluid temperature that alters drilling fluid density and viscosity, as well as changes near-wellbore formation temperature. Temperature changes in the near-wellbore formation need to be understood so that useful interpretation of often available temperature data from multiple discrete temperature sensors (MDTS) may be made.

In deepwater assets, fluid circulation through cold water makes the problem more complex. Deepwater drilling operation could be viewed as consisting of four processes: (1) mud circulation in the riser affected by surrounding cold sea water; (2) mud circulation in the cased and cemented zone; (3) mud circulation through the target zone (open hole); (4) shut-in after drilling through the target zone. Forced convective heat transfer dominates in the first three processes while conductive heat transfer is dominant during the shut-in period. Estimating temperature in the wellbore during and after circulation is critical for mud rheology, tubular thermal stress, and cement design. Application of “rule-of-thumb” and/or complicated numerical simulation is often unreliable and/or impractical.

This paper presents analytic models to estimate temperature profile during and after drilling fluid circulation in deepwater environment. Steady heat transfer is assumed in during fluid circulation, and transient modeling is performed for shut-in periods. Energy balance is set up over the differential control volume to develop the models. The end of circulation would provide the initial condition for the shut-in period. The models are used to estimate bottomhole temperature distribution during and after circulation. The analytical model is verified using data from a real deepwater well that had permanent downhole gauges (PDGs) installed at the bottomhole.

Commentary by Dr. Valentin Fuster
2018;():V008T11A024. doi:10.1115/OMAE2018-78732.

Well construction relies on metal pipes called casing to maintain its integrity during the life of the well. From surface to the target depths the inserted casings are used to prevent well collapse, hence being exposed to external pressure loads. Also the casing in place must hold the internal pressure during well operations, which is called burst resistance. During the past decades the manufacturing process of casing and tubing has been dramatically improved, but their testing has suffer very little changes. It is known to date that API calculation of collapse resistance is very conservative, most of the modern pipe mills being able to deliver pipes with higher collapse pressure than API calculated values. The paper will describe the actual testing procedure of collapse testing of pipes and critically discuss about the human error that is introduced during these measurements. The results shows that only through high quality laboratory standards, such errors can be mitigated, while automation must be carefully considered.

Commentary by Dr. Valentin Fuster
2018;():V008T11A025. doi:10.1115/OMAE2018-78776.

Standardisation is the process of developing a standard at an international, regional or national level. The oil and gas industry welcomes international standards as tool to do its operations efficiently and responsibly, and to demonstrate to comply with regulations, where applicable. In this way, the oil and gas industry uses international standards as part of their licence to operate. Because the oil and gas industry is acting globally, it would like to prevent that they have to deal with different standards depending on the region or country in which they operate. Therefore, the oil and gas industry strives for international standards that are also adopted as national standards across the world. The European oil and gas industry supports this vision by adopting the international standards as European standards, which will then become the national standard as well in 34 European countries at once. Also in the field of offshore structures and more recently Arctic operations, international standards are being developed or revised to respond to the needs of the industry. These standardisation activities include European involvement to ensure alignment of the standards portfolio of the oil and gas industry.

Commentary by Dr. Valentin Fuster

Petroleum Technology: Inflow Control Technology in Reservoir Management

2018;():V008T11A026. doi:10.1115/OMAE2018-77223.

Autonomous Inflow Control Device (AICD) completion was successfully designed and applied in a horizontal well drilled in a deep reservoir in an extra heavy oil field located in South America where the average total depth of the targeted reservoir is around ten thousands feet and the in-situ viscosity is 600 cps while API Gravity is ranged between 8.5–9.5.

Due to geological and petro-physical features in this area which turns into permeability variations and thick transition zone across the reservoir, a horizontal well of 2500 feet length was drilled and completed with a standalone screen along with Autonomous Inflow Control Device (AICD) to avoid sand production and delay water production. The initial design for the AICD considered the variation of permeability, rock quality, pressure differential across the horizontal length including the operational factors. Accordingly, multiple scenarios using reservoir simulation built-in model (Petrel-RE) and Netool for ICD selection, design and placement where the geological properties of the model were updated based on the run NMR and Caliper logs while geo-steering the well. Also, a fine grid sector model was generated to assess optimum well completion design.

The AICD completion was successfully deployed and resulted in extending the well life by delaying water production and it is expected to get its ultimate benefit whenever starting the implementation of a water flood project near that producer well.

Topics: Oil fields , Inflow
Commentary by Dr. Valentin Fuster
2018;():V008T11A027. doi:10.1115/OMAE2018-78342.

Water logging problem in late production reservoir with abundant edge-bottom water and water-gas layer stagger is one of the main factors that lead to production wells stop flow. For the water plugging problem during gas well production, the common operation is coiled tubing through casing. So, coiled tubing technology without moving production string is explored.

X oilfield is located in Sichuan basin of China southwest and belongs to the origin of gas pipeline from Sichuan to China east. Its main gas producing area is carbonatite full of edge water and controlled by structural and lithology. The relationship between water and gas is complex and water-gas system is independent of different blocks and different layers. Because the main gas producing layer is close to the water layer, lots of gas producing wells stop spray for high water cut. At the meantime, the difficulty and risk of water plugging increases for its high depth of main gas producing layer and high temperature at the well bottom.

To solve the problem above, cement slurry system with the characteristics of high temperature and sulfur resistant and channeling preventing is developed. At the same time, the cement slurry system has low friction and high liquidity and is easy to flow through the coiled tubing. Besides, cement slurry pollution is reduced and the success rate of gas well produced water plugging is improved by the combination of coiled tubing and cementing process and the construction technology optimization, software simulation and laboratory evaluation is carried out. The key step is that log analysis of water and gas distribution is done first. Then, tubing-expansion bridge plug is placed under the water layer and the cement slurry is sent to the desired location. At last, coiled tubing is put down after cement solidification and gas production is recovered.

The measurement of coiled tubing and cement slurry system is positive for water plugging in gas wells with high depth and temperature. The oilfield test results show that daily gas production is improved largely and liquid production is reduced by 90% of 4 wells with high water cut through water plugging. Besides, operation cost is reduced and the pollution problem caused by produced water is also solved, which can provide certain significance for the same type wells need water plugging operation.

Topics: Wells , Tubing , Water
Commentary by Dr. Valentin Fuster
2018;():V008T11A028. doi:10.1115/OMAE2018-78580.

There are many different types of smart well systems such as Inflow Control Valves, Inflow Control Devices and autonomous devices of various designs. The most common inflow system is blank pipe, producing through a screen and into the control valve at the connection sub.

To control the functionalities one may use surface control lines, dropping balls or darts or simply let the valves react autonomously to changes downhole. These tools can be deteriorated by erosion, plugging of fines, plugging of of heavy oil residue or by scaling.

Scaling is a complicated issue as it often builds up near critical parts of the tool, changing the flow pattern and affecting or offsetting the flow assurance. This paper will present a new concept in chemical well injection. It is proposed to connect a capillary tube through the entire completion string to inject chemicals to prevent scaling of critical tools before the oil enters the tool, thereby increasing the time the tool will function.

A new downhole chemical injection valve is developed. It is located near the injection point to prevent U-tube pressure effects often associated with surface injection systems. This injection valve can also easily be adjusted downhole or shut off if required. The advent of water production often changes chemical injection requirements. The new system can accommodate any changes in chemical or flow rates. The system is fully mechanical and does not rely on electrical control cables. Flow regulation is performed through the capillary tube.

The paper will describe the new downhole chemical injection system and its application to smart well technology.

Commentary by Dr. Valentin Fuster
2018;():V008T11A029. doi:10.1115/OMAE2018-78724.

Maximum stabilized water-cut (WC), also known as ultimate water-cut in a reservoir with bottom-water coning, provides important information to decide if reservoir development is economical. To date, theory and determination of stabilized water-cut consider only single-permeability systems so there is a need to extend this concept to Naturally Fractured Reservoirs (NFRs) in carbonate rocks — known for severe bottom water invasion. This work provides insight of the water coning mechanism in NFR and proposes an analytical method for computing stabilized water-cut and relating to well-spacing design.

Simulated experiments on a variety of bottom-water hydrophobic NFRs have been designed, conducted, and analyzed using dual-porosity/dual-permeability (DPDP) commercial software. They show a pattern of water cut development in NFR comprising the early water breakthrough and very rapid increase followed by water cut-stabilization stage, and the final stage with progressive water-cut. The initial steply increase of water-cut corresponds to water invading the fractures. The stabilized WC production stage occurs when oil is displaced at a constant rate from matrix to the water-producing fractures. During this stage water invades matrix at small values of capillary forces so they do not oppose water invasion. In contrast, during the final stage (with progressing water cut) the capillary forces grow significantly so they effectively oppose water invasion resulting in progressive water cut.

A simple analytical model explains the constant rate of oil displacement by considering the driving effect of gravity and viscous forces at a very small value of capillary pressure. The constant oil displacement effect is confirmed with a designed series of simulation experiments for a variety of bottom-water NFRs. Statistical analysis of the results correlates the duration of the stabilized WC stage with production rate and well-spacing and provides the basis for optimizing the recovery. Results show that stabilized water-cut stage does not significantly contribute to recovery, so the stage needs to be avoided. Proposed is a new method for finding the optimum well spacing that eliminates the stabilized WC stage while maximizing recovery. The method is demonstrated for the base-case NFR.

Commentary by Dr. Valentin Fuster

Petroleum Technology: Innovations in Drilling, Production, and Transport

2018;():V008T11A030. doi:10.1115/OMAE2018-77120.

Due to the inconvenient maintenance and high costs of subsea flowmeters, virtual subsea flow metering technology is developed for subsea gas condensate fields, especially for marginal fields. In this paper, virtual subsea flow metering technology is introduced, the advantages are summarized, and international virtual metering products are listed. For a typical gas field virtual subsea flow metering system, the configuration, input and output data, as well as flow models and calculation methodology is explained. A virtual flow metering field application case in a subsea tieback gas condensate field in offshore China is introduced, from the project background to the application execution and finally the results. The virtual metering results met well with gas field data and showed great robustness by continuously working on the site.

Commentary by Dr. Valentin Fuster
2018;():V008T11A031. doi:10.1115/OMAE2018-77550.

The temperature is very interesting phenomena in the well system. Due to the geo-thermal gradient induced by the core of the earth, deeper well means higher temperature. The wellbore temperature during drilling depends on many factors such as wellbore geometry, wellbore depth, flow rate, the properties of the formation, the properties of the fluid, the geothermal gradients etc. Analytical modeling is very helpful to understand the heat phenomena in the well system and how the thermal effects are working in the well system. In this paper, two analytical modelings are investigate to discover how the temperature distributes in the wellbore. Some sensitivity analyses are calculated.

Commentary by Dr. Valentin Fuster
2018;():V008T11A032. doi:10.1115/OMAE2018-78328.

Water-based drilling mud is one of the commonly used fluid systems for drilling operations. The loss of drilling fluid in porous media and fractured formations have been one of the industry’s focus in the past decades. However, the dynamics and constantly changing wellbore conditions push the boundaries for more research into accurate quantification and mitigation methods for fluid loss. In the design and development of drilling fluids, most test conditions are kept constant during fluids property testing. Drilling fluid loss and rheological parameters are determined experimentally at constant test conditions, and according to the combination of mud additives, rather than a comprehensive approach. In addition, conventional methods of quantifying drilling fluid loss properties for field application can be is time-consuming, considering that multiple factors impact fluid loss.

This study presents a statistical engineering approach for pore-scale characterization of water-based mud (WBM) invasion. The methods used in this research are: special case of factorial design of experiment (DoE), analysis of variance (ANOVA), and regression. Important field parameters based on previous studies and industry recommendations were carefully integrated in the DoE and result analyses. These parameters include but not limited to: porous media type, temperature, type of lost circulation material (LCM), concentration of LCM, drilling string rotary speed, and eccentricity. Ceramic filter tubes were used for the first set of experiments and Upper Grey sandstone rock samples were used for the second set of experiments. The statistical analyses performed in this study were based on a 95% confidence interval (CI). The results show that for single factor interpretation, increase in temperature and rotary speed increased dynamic fluid invasion significantly. Increase in LCM concentration resulted to a significant decrease in fluid invasion. LCM concentration and rotary speed interaction revealed a significant decrease in fluid invasion. LCM concentration and temperature interaction significantly increased fluid invasion. Rotary speed and temperature interaction also increased fluid invasion significantly. The three-factor interaction effect of LCM concentration, rotary speed, and temperature was not significant in reducing fluid invasion. For the conditions used in this study, the regression analysis showed that dynamic fluid invasion in Upper Grey sandstone can be explained from variation in LCM concentration and rotary speed. The results and methods from this study can provide reliable information for drilling fluids design and selecting operating conditions for field application.

Topics: Fluids , Drilling
Commentary by Dr. Valentin Fuster
2018;():V008T11A033. doi:10.1115/OMAE2018-78541.

Mud pumps are essential components of the drilling rig, since they support the drilling process, and are required to operate 24/7. Their ability to generate high pressure at relatively high flow rates led to a wide application of reciprocal pumps, from mud pumps to fracking pumps, within the oil and gas business. The elements of the mud pump, especially the mud pump valve, are exposed to erosion-corrosion processes during the pumping operations because of the solids and the corrosive components of the pumped fluid which leads to a drastically reduction of their durability. The downtime of such a pump may add high costs to the drilling or fracking operations, and any improvement of the components durability helps. The mud circulation system is of main interest during the drilling operation, with 7% of the personnel time being spent on mud pumps and 26% on monitoring from the total time spent in the mud area. The present paper shows the experimental results regarding the hard metal deposition of high erosion/abrasion resistance materials on the valve seat’s working surfaces, and the use of the welding process in order to increase their durability, and eventually, to establish the possibility of reconditioning the mud pump valve. The experiments were performed on used valves as part of their reconditioning process, but can also be performed on new elements, as means to increase the durability and erosion resistance. The results are very promising and show a good and strong hard metal deposition with very good mechanical properties. The paper describes the steps and the specific pre and post welding treatment in order to achieve the optimum hard-facing parameters.

Commentary by Dr. Valentin Fuster

Petroleum Technology: Integrity of Well Barriers

2018;():V008T11A034. doi:10.1115/OMAE2018-77215.

The oil and gas industry, by default, has been pretty conservative when it relates to innovation and drastic changes in mind-set. Mainly focused on the costly drilling and completion steps, some of the “smaller” services have been ignored. As such, Repsol has decided to take a deeper look at nano and micro sensored technologies in other industries and potentially replicate some of this innovation, allowing the industry to take “a step” closer to smarter zonal isolation. In general, the industry is quite aware of well integrity issues that we face. Be it immediate (whilst drilling/completing), within the life of production or even during the abandonment phase. There are many statistics proving that on a global scale, there are well integrity and sustained casing pressure issues on about 30–60% of all drilled wells. And we can confirm that a majority of these are directly related to well-cementing, creating an immense impact(s), that can negatively influence overall HSE, loss of potential reserves and bottom line dollar-amount. The ability to take a close look at well cementing has only proven feasible in a laboratory environment, beyond that, the knowledge and prediction of the actual state of the zonal isolation has proven difficult, confusing or costly. Regardless of the improved best practices, enhanced logging tools or state-of-the-art technological advances in chemicals/systems — we still seem to have that unanswered “gap” — on what actually happened, when it happened and how to avoid it in the future. This paper describes the background, the thought process and the potential advantage of ours proposed ideology, let Alone ongoing R&D efforts to improve the cement isolation quality, measurements and real time monitoring of its properties and integrity during the well life and after abandonment by sensoring it and communicating back to surface.

Commentary by Dr. Valentin Fuster
2018;():V008T11A035. doi:10.1115/OMAE2018-77493.

The AUSMV scheme is a hybrid transient model derived from Advection-Upwind-Splitting Method (AUSM) and Flux Vector Splitting (FVS) method. The two-phase flow model was formulated under isothermal condition. This neglected the behavior of temperature during transient scenarios, for instance, unloading and drilling fluid circulation. In contrast to this assumption, wellbore temperature changes locally with time under such dynamic conditions.

The numerical accuracy of the AUSMV scheme can be improved in two ways. The scheme can be reformulated by including energy equation in the system of governing conservation laws. This option, however, is computationally rigorous and expensive. A better alternative is to develop a separate dynamic temperature model that will calculate wellbore and formation temperatures. Then the two dynamic models — the AUSMV scheme and temperature model — are numerically coupled into a thermohydraulic simulator.

The present work will include a brief introduction to the AUSMV scheme, followed by the description of the temperature model. In addition, how the two transient models are integrated will be presented.

Simulation cases, demonstrating the improved modeling capability of the scheme for a drilling situation, will be shown.

Topics: Temperature
Commentary by Dr. Valentin Fuster
2018;():V008T11A036. doi:10.1115/OMAE2018-78254.

In order to effectively compensate for bulk shrinkage of cement systems, the reaction of expansive additives must be regulated taking into account the development of cement hydration. In this study, nano-MgO particles (NM) with controlled reactivity were added to a cement system. The reactivity of NM was regulated via heat-treatment and the cement systems were investigated using isothermal calorimetry. Our results showed that increase in heat-treatment temperature resulted in coarsening of the NM and retardation of the NM reaction. We demonstrated that the addition of NM, heat-treated at low temperature, to a cement system caused significant reduction in the induction period compared to the reference system without NM. Controlling the reactivity of NMs might be a promising method in designing zero-shrinkage cement systems.

Commentary by Dr. Valentin Fuster
2018;():V008T11A037. doi:10.1115/OMAE2018-78305.

In this work, we have studied rheological behavior and mechanical properties of selected modified rock-based geopolymer, which are suggested for zonal isolation and permanent abandonment of hydrocarbon wells. Our rheological measurements of the geopolymeric slurries shows a very small Yield Stress and a constant plastic viscosity. Even though the yield stress is small, a non-Newtonian flow behavior is distinguished. Mechanical vibration measurements showed that vibrations have surprisingly little effect on the shear stress changes. Consistency of the geopolymeric slurry was measured by utilization of atmospheric and pressurized consistometers to find the impact of pressure and temperature on pumpability. A temperature decrease of 10°C postponed the geopolymerization by 4 hours and a temperature increase by 10°C accelerated the geopolymerization by 30 minutes. Static-fluid-loss test showed only 1.6 (ml) of fluid loss after 30 minutes which is another advantage of the geopolymeric slurry. The elastic shear wave and compressional wave velocities and velocity anisotropies of the samples were tried to be determined experimentally. However, our efforts showed that geopolymeric structure of the samples requires different frequencies as it damps the high frequency signal.

Commentary by Dr. Valentin Fuster
2018;():V008T11A038. doi:10.1115/OMAE2018-78309.

Cement evaluation tools have been used in the oil industry for decades to examine the integrity of cement bonding to the well casing and openhole. It has been suggested that such tools also can be used to verify the presence of a crept shale formation that has formed a barrier outside the casing. However, the ability of these tools to help determine an acceptable leakage risk level, which results from sufficient hydraulic isolation outside and between casing remain a subject of dispute from experiences in the industry. In this paper we present results from ongoing research that may help contribute to resolving this dispute. The research objective is to design and build a ’shale as barrier’ reference calibration cell. The reference cell is to be designed and made accessible to existing and emerging annulus barrier evaluation methods. The purpose is to help increase the quality of decisions made from such barrier evaluation technologies in an explicit well plug and abandonment context. The technical complexity of dispute coupled to the voice of business and stakeholder interests have been identified as a factor that could make project execution challenging. As result, a method to assist the execution of the project has been developed to systematically assure necessary stakeholder and end-user involvement. In this paper we present the method and demonstrate its application as an useful basis for project decision making and documentation. The method focuses on the capture and treatment of stakeholder preference elicitation, which is framed by traditional stages defined in the reference cell development process by adopting the concept of quality function deployment.

Topics: North Sea , Shales
Commentary by Dr. Valentin Fuster
2018;():V008T11A039. doi:10.1115/OMAE2018-78696.

The annular cement sheath is one of the most important well barrier elements, both during production and after well abandonment. It is however well-known that repeated pressure and temperature variations in the wellbore during production and injection can have a detrimental effect on the integrity of the cement sheath. Degradation of cement sheaths result in formation of cracks and microannuli, which leads to loss of zonal isolation and subsequent pressure build-up in the annulus. It is therefore important to study and understand cement sheath failure mechanisms to prevent such barrier failures.

A unique laboratory set-up with downscaled samples of rock, cement and pipe has been constructed to study cement sheath failure mechanisms such as radial crack formation and debonding during pressure cycling. Cement integrity before and after pressure cycling is monitored by X-ray computed tomography (CT), which enables 3D visualization and quantification of radial cracks formed inside the cement sheath as well as debonding towards casing and formation.

This paper describes this laboratory set-up in detail. Furthermore, some preliminary experimental results are also included that demonstrates the applicability and functionality of the new set-up.

Commentary by Dr. Valentin Fuster
2018;():V008T11A040. doi:10.1115/OMAE2018-78707.

One of the most critical operations during well construction is the cementing procedure, where drilling fluid is displaced by cement, normally with one or more spacer fluids in between. Due to the curing nature of the cement slurry there will be only one opportunity to cement the well properly. Although one for top hole cases can fill cement in from the top in a remedial operation, this possibility cannot fully compensate for a non-optimal initial cement job. Furthermore, it cannot be applied to other well sections. In those sections, complex squeeze cementing operations may be necessary. Consequences of improper annular cement can be leakage during production phase and extensive costs when the well is to be plugged for abandonment after the production phase. To ensure that the risk of poor cement is minimised it is important to use the best procedures to place the cement properly. Most models in use assume that the annulus is homogeneous. This is not always the case since washout sections appear during drilling. The effects of these on cementing are not sufficiently studied and considered in models and procedures.

Here we present and discuss results from fluid displacement experiments in a laboratory flow loop, illustrating annular displacement of drilling fluid by spacer (or spacer by cement). Model fluids with realistic densities and rheological properties have been used in a test setup with a transparent annular section. The wellbore is represented by a 10 m long test section, where the annulus has a 6,5” outer diameter and an inner string of 5” that can rotate. A washout section is represented by a 2 m long section of the outer pipe with a larger diameter of 11”. These diameters are representative for the lower parts of a well were high wellbore inclinations are common. In these sections the inner pipe cannot be assumed concentric at all times, so both concentric and eccentric positions have been tested. Experiments reported here were conducted at 60 degrees inclination. The test section was instrumented with conductivity probes in an array around the perimeter at 4 separate positions along the pipe, including the inlet and outlet of the washout section. Together with a camera along the test section, this provided information about the motion and shape of the liquid-liquid interface through the test section.

Results show that the displacement front changes significantly when entering the washout zone compared to the regular annular section. Due to the larger flow area the density differences between displaced and displacing fluids become more important in the washout section, while momentum effects dominate in the regular section.

Topics: Fluids , Displacement
Commentary by Dr. Valentin Fuster

Petroleum Technology: Petroleum Production Systems Design and Operation

2018;():V008T11A041. doi:10.1115/OMAE2018-77017.

The aim of this work was to compare the efficiency of a biosurfactant (BS) and a commercial surfactant under post-salt and pre-salt reservoirs conditions, to evaluate their potential use to EOR (Enhanced Oil Recovery). Rhamnolipids BS from Pseudomonas aeruginosa (INCQS 4046), were produced [1] and characterized [2], [3], and Ultrasperse II® was purchased. Calcite flotation test was conducted to access wettability reversal [4]. IFT analysis was performed [5] under controlled pressure, temperature and salinity to simulate post-salt and pre-salt environmental conditions. Central Composite Rotational Designs (CCRD) were analyzed [6]. According to results, it was demonstrated that both products can reverse wettability and are even more effective under post-salt and pre-salt reservoirs environmental conditions. However, rhamnolipids present better potential for use, since it was more effective when compared to the commercial surfactant, attaining lower interfacial tension values and higher reversal wettability percentages using lower concentrations of product.

Commentary by Dr. Valentin Fuster
2018;():V008T11A042. doi:10.1115/OMAE2018-77073.

The construction of subsea wells under deep water depths brought the necessity to understand the behavior of columns on such conditions. These columns can be risers, drill strings or casing strings, which are either being installed by lowering them until they reach the sea bottom and/or inside the well, or they are already connected and fully operational. Since these columns are exposed to the open sea, environmental loads such as waves and currents will affect them. Depending on how harsh these environmental conditions are, drilling operations may be suspended. Therefore, understanding how such loads interact with such columns are of the utmost importance if one wants to ensure operational safety. In this paper, we discuss about the problem of emergency disconnections of risers. The concern of doing an emergency disconnection is fundamental for ensuring operational safety because the well will lose a safety barrier, as the level of the drilling fluid inside the well can no longer be controlled after the riser is disconnected, and thus the fluid cannot maintain its downhole pressure anymore. This work focuses on a finite elements modeling of riser dynamics, with the appropriate applied loads, to verify under which sea conditions the riser must be disconnected. The result of such analysis is called an “operational map”, which displays the maximum values of stress along the riser as a function of different sea conditions. Using the riser material properties, this map can then be divided in two regions — failure and admissible — and thus one can see for which sea conditions the riser must be disconnected to avoid its failure. The contribution of the present study is proposing a methodology to elaborate an operational map for a given riser scenario, from which both failure and admissible regions can be seen for emergency disconnection operations.

Commentary by Dr. Valentin Fuster
2018;():V008T11A043. doi:10.1115/OMAE2018-77792.

A Giant Heavy Oil Field requires extending and maintaining the production plateau during a continuous period of more than 30 years. In order to increase the revenues of the global project, the construction of Upgrader plant is always considered.

Cold production conditions are first, the project has estimated between 10-8% of the STOIIP obtained through cold production but it would not be enough to extend the production plateau. Therefore, later on it will be necessary to apply thermal EOR techniques, as:

• Steam Injection: 1-CSS + Steam Flooding, 2-SAGD or HASD

• In-situ combustion

Aim for this integrated study was to visualize the new facilities design and modification on the exiting cold production facilities to manage the hot production (investments) in function of reservoir/production requirements. The benefit of this integrated study is to value the additional investments in surface facilities required under thermal EOR production to get the global integrated project evaluation.

Commentary by Dr. Valentin Fuster
2018;():V008T11A044. doi:10.1115/OMAE2018-78323.

Two-phase vertical flows are of utmost importance for petroleum production, since underground petroleum reservoirs produce oil and gas simultaneously, which must flow together upward to the sea floor through wells, and from these to the production floating units through suspended pipes (risers). Along the pipelines, the mixture of oil and gas may develop several flow patterns — such as bubble, slug, churn and annular flow. These physical configurations present specific characteristics that demand distinct modeling of the head loss as a function of the flow rate. The correct characterization of the flow patterns, under given operational conditions, is fundamental to the modeling of the dynamics of the flow and to the relation between head loss and flow rate. In the literature, most studies on the establishment of the flow patterns have been carried with water and air, and have been restricted to the case of static pipes, while production risers are in constant movement due to the action of waves, sea currents and the displacement of the floating production unit. In the present work, an experimental study of vertical two-phase flow of water and air is conducted with the oscillatory movement of a long and slender flexible vertical pipe of 8,0 m of length and 25,4 mm of diameter. The head loss is measured for different frequencies of oscillation. Comparisons are made between the static and oscillating pipe, with regard to the flow patterns and head losses. The effect of the frequency of oscillation is detected.

Topics: Pipes , Two-phase flow
Commentary by Dr. Valentin Fuster
2018;():V008T11A045. doi:10.1115/OMAE2018-78359.

Polymer flooding dates from the 1960s. Early applications targeted onshore medium-to-heavy oils up to 100 cP, with limited reservoir temperature and water formation salinity. The number of implemented polymer flooding projects followed oil prices. Since its early days, polymer flooding had overcome many technical obstacles. Advances in polymer manufacturing technology, cost reduction and the use of horizontal wells have pushed polymer flooding as a feasible EOR method. A better understanding of the physical phenomena associated with polymer flow through porous media and technology advancement have extended polymer flooding applications to more viscous oil, higher salinity, and temperature level, as well as to offshore prospects. Meaningful advantages of polymer flooding over conventional methods are consolidated in the literature, such as oil recovery anticipation, incremental oil recovery and reduced volumes of injected and produced water to reach a target recovery factor. Despite all technological advances, polymer flooding needs to be tailored for the specific conditions of the target reservoir. Collect and integrate laboratory, simulation, and field information are essential for a successful polymer flooding application. This paper aims to correlate critical information to the various stages necessary for polymer flooding evaluation and production forecast. First, successfully implemented field cases allow the establishment of ranges for the method application. Once the applicability of polymer flooding is certified, the polymer solution to be injected is designed according to the reservoir characteristics and target conditions. Laboratory tests are performed to determine phase mobilities, polymer retention, and polymer degradation. These parameters are assessed through different experiments, and normalized variables provide data integration. Once the required parameters are determined, it is possible to build a base simulation model. History matching this base model to the laboratory data certifies its validity. An upsized analysis of this model is required to include some degradation phenomena. The 1D laboratory model is extended to a 3D model that incorporates permo-porosity distributions to analyze well characteristics in their radius of influence. The final step is large scale simulation and production forecast. Data integration along each stage and among then all allow the tailoring of the polymer flooding to EOR. The use of normalized parameters to evaluate the results is useful for analysis at different scales, from the laboratory to the reservoir. The proposed workflow can contribute to the design, planning, evaluation, and implementation of polymer flooding in a target field.

Commentary by Dr. Valentin Fuster
2018;():V008T11A046. doi:10.1115/OMAE2018-78384.

Integrated analysis of reservoir and production system models for field development can improve production forecasts. This integration allows the evaluation and optimization of parameters of both systems for both financial return and accurate production prediction. This work evaluates the presence and position of manifolds and their influence on production. We use a Brazilian benchmark case to perform an integrated analysis of oilfield production evaluating the influence of various aspects of manifold systems to increase financial return. The results showed that integrated analysis of optimized manifold locations and the number of connected wells improved financial return. Thus, we recommend the inclusion of this integrated production modeling in field management.

Commentary by Dr. Valentin Fuster
2018;():V008T11A047. doi:10.1115/OMAE2018-78565.

A notable trend in the realm of oil production in harsh environments is the increasing use of Electrical Submersible Pump (ESP) systems. ESPs have even been used as an artificial-lift method for extracting high-viscosity oils in deep offshore fields. As a way of reducing workover costs, an ESP system may be installed at the well bottom or on the seabed. A critical factor, however, in deep-water production is the low temperature at the seabed. In fact, these low temperatures constitute the main source for many flow-assurance problems, such as the increase in friction losses due to high viscosity. Oil viscosity impacts pump performance, reducing the head and increasing the shaft power. This study investigates the influence of a temperature increase of ultra-heavy oil on ESP performance and the heating effect through a 10-stage ESP. Using several flow rates, tests are performed at four rotational speeds and with four viscosity levels. At each rotational speed curve, researchers keep constant the inlet temperature and viscosity. The study compares the resulting data with a simple heat model developed to estimate the oil outlet temperature as functions of ESP performance parameters. The experimental data is represented by a one-dimensional model that also simulates a 100-stage ESP. The simulations demonstrate that as the oil heat flows through the pump, the pump’s efficiency increases.

Commentary by Dr. Valentin Fuster

Petroleum Technology: Well Drilling Fluids and Hydraulics

2018;():V008T11A048. doi:10.1115/OMAE2018-77056.

Smart drilling fluids, which can change their properties according to the flow environment, must be carefully designed so that they can handle the difficult challenges of HP/HT drilling successfully. Due to their unique physico-chemical properties, nanoparticles (NP) are considered as very good candidates for the formulation of these smart drilling fluids. This study presents filtration and rheological results of newly developed high-performance water-based drilling fluid systems containing different nanoparticles, commercial (C) titanium oxide (TiO2) and commercial (C) copper oxide (CuO) NP and compares them with results from using custom-made (CM) iron oxide (Fe3O4) NP and commercial (C) iron oxide (Fe3O4) NP, previously reported.

Novel nano-based drilling fluids were made of de-ionized water, 7 wt% commercial Na-bentonite (base fluid), and NP were added at 0.5 wt%. The rheological properties of the produced suspensions were measured at temperatures up to 60°C and at atmospheric pressure with a Couette-type viscometer. Filtration characteristics were determined at elevated pressures and temperatures in a HP/HT filter press (500 psi/176°C) using ceramic discs as filter media, of permeability, k = 775 mD.

The results of this study showed that the samples containing 0.5 wt% C TiO2 caused a reduction in the fluid loss by 23%, while C CuO NP resulted in 16% reduction, when compared to that of the base fluid, at these HPHT conditions. This should be compared to the 47% and 34% reduction in fluid loss of 0.5% CM Fe3O4 NP and of 0.5% of C Fe3O4 NP, reported previously.

Analysis of rheological data revealed shear-thinning behavior for all the tested novel drilling fluids. The samples containing TiO2 and CuO NP exhibited a yield stress less than that of the base fluid, compared to the increased yield stress observed for the C and CM Fe3O4 NP. This behavior can be attributed to the fact that TiO2 and CuO NP may also act as deflocculants and prevent the gelation of bentonite suspensions.

This study shows that commercial nanoparticles of TiO2 and CuO do not perform as well as the Fe3O4 NP on filtration but provide drilling fluids with lower yield stresses, thus they could be considered as alternatives to Fe3O4 in situations where the rheological properties are critical.

Commentary by Dr. Valentin Fuster
2018;():V008T11A049. doi:10.1115/OMAE2018-77105.

Downhole torque measurements have become an inherent part of MWD (measurement while drilling) systems. It allows drilling engineers to estimate the downhole friction and detect the presence of obstructions, for instance, cuttings bed caused by insufficient cuttings transport. The latter is a big concern when drilling horizontal and extended-reach wells.

This paper describes a method of well friction analysis as a function of adjustable drilling parameters and parameters that describe moving cuttings dune. Experiments are performed in a pipe with an internal diameter of 0.04 m and 5° inclination from the horizon, which represents a wellbore. An inside rotating pipe with an outer diameter of 0.025 m simulates a drillpipe, with a possibility of rotating speed from 0 to 1000 RPM (revolutions per minute). Glass pellets are used to simulate and display cuttings behavior in the wellbore. An electric motor is used to provide rotation of the drillpipe, supplied with an encoder to measure the electric current associated with the torque. The measurements are used to calculate the torque loss over the studied pipe length. A high-speed camera installed outside the outer pipe allows capturing images of the height of the particle bed as well as the pipe eccentricity, which increases with distance from the origin (rotating mechanism) due to the pipe’s weight and inclination.

The combined effect of these factors on the kinetic friction between the outer and inner pipes is investigated in this paper. Ultimately, the friction factor is calculated by equating measured motor torque to the theoretical torque.

The main objective of the study is a development of a methodology to express the friction factor in terms of adjustable drilling parameters in an environment, complicated with the presence of moving cuttings bed and varying pipe eccentricity. This study can supplement other research that is aimed to improve understanding of the intricate phenomenon of the wellbore friction.

Topics: Wells , Modeling , Pipes
Commentary by Dr. Valentin Fuster
2018;():V008T11A050. doi:10.1115/OMAE2018-77203.

Drilling fluids are visco-elastic materials, i.e. they behave as a viscous fluid when subject to a sufficient shear stress and like an elastic solid otherwise. Both their elastic and viscous properties are time-dependent, i.e. drilling fluids are thixotropic. Because of thixotropy, it takes a finite time before the effective viscosity of a drilling fluid attains an equilibrium when the fluid is subject to a change of shear rate. This effect is visible when one changes the applied shear rate in a rheometer, as the fluid will gradually adapt to the new shearing conditions.

When the velocity of a drilling fluid changes, for instance due to a change in pump flow rate, movement of the drill string, or change of flow geometry, the fluid will exhibit a time-dependent response to the new shearing conditions, requiring a certain time to reach the new equilibrium condition.

Unfortunately, the time-dependence of the rheological properties of drilling fluids are usually not measured during drilling operations and therefore it is difficult to estimate how thixotropy impacts pressure losses in drilling operations. For that reason, we have systematically measured the time-dependence of the rheological properties of several samples of water-based, oil-based and micronized drilling fluids with a scientific rheometer in order to capture how drilling fluids systems respond to variations of shear rates.

Based on these measurements, we propose to investigate how one existing thixotropic model manages to predict the shear stress as a function of the shear rate while accounting for the shear history and gelling conditions. Then we propose a modified model that fits better, overall, with the measurements even though there are still noticeable discrepancies, especially when switching back to low shear rates.

Commentary by Dr. Valentin Fuster
2018;():V008T11A051. doi:10.1115/OMAE2018-77266.

The paper presents the results of modeling the steady-state flow of drilling fluid with cuttings in an annulus for the flow regimes typical for horizontal drilling. The studied parameters include effects like fluid rheology, drillstring rotation and eccentricity on flow regime, pressure drop and cuttings bed.

It has been demonstrated that increasing the drilling fluid’s effective viscosity increases the pressure drop, but it decreases the cuttings bed area, while drillstring rotation significantly changes the flow structure, improving cuttings transport and reducing the pressure drop. The considered flow structure can change abruptly due to changed drill string positioning and rheological fluid properties. Such structural changes are followed by abrupt changes in the pressure drop and cuttings bed area.

Commentary by Dr. Valentin Fuster
2018;():V008T11A052. doi:10.1115/OMAE2018-77275.

Drilling equipment tests during field operations are always affected by uncertainties and variations regarding the local conditions in the borehole. In order to provide a more controlled testing environment for research, a hardware simulator was established at the Drilling Simulator Celle, Clausthal University of Technology. The simulator replicates the last 25 meters of a horizontal borehole and permits the drilling of a five-meter long rock sample. The setup includes a flow loop with two pumps for borehole cleaning and cuttings transport during the drilling process. During operation, temperature of the fluid increases due to pressure losses in the loop.

This paper introduces a basic model to determine the maximum allowable continuous operation time of the hardware setup. Further improvements can be achieved by doing sensitivity analyses of the parameters affecting the system behavior, e.g. ambient temperatures or mass flow rate. Measurements from the hardware setup are used for validation of the model and show consistent results.

Commentary by Dr. Valentin Fuster
2018;():V008T11A053. doi:10.1115/OMAE2018-77321.

Experimental investigation of flow field past a spherical particle settling in viscoelastic fluids using particle image shadowgraphy techniques studies have shown that the settling velocity of particles in viscoelastic fluids decreased significantly with the increasing elasticity of the fluids. However, our understanding of how and why the change in fluid elasticity influences the particle settling velocity are not yet fully developed. An experimental study, therefore, has been conducted to understand the reasons behind why the settling velocity of the particles decrease with the increasing fluid elasticity. The main objectives were: (i) to investigate the fluid flow field behind the settling particle by using particle image velocity (PIV) technique; (ii) to understand the changes caused by the elasticity of the fluid on the flow field past the settling particle; (iii) more specifically, to determine how the fluid velocity profile and the resultant drag forces acting on the settling particle change with the increasing fluid elasticity.

Two different viscoelastic fluids were formulated by mixing 3 grades of HPAM polymer (MWs: 500,000; 8,000,000; 20,000,000; concentrations: 0.09% and 0.1%wt). The fluids were designed to have almost identical shear viscosity but significantly different elastic properties. The shear viscosity and elasticity of the fluids were determined by performing shear viscosity and frequency sweep oscillatory measurements, respectively. The settling velocities of the spherical particles in viscoelastic polymer fluids were measured by using particle image shadowgraph technique. The fluid flow field behind the settling particle was determined by using the PIV technique.

Results of the PIV measurements demonstrated that negative wakes were present in viscoelastic fluids. The stagnation point (i.e. the point where the velocity becomes zero and above that the fluid starts moving in the direction opposite to the particle movement) was closer to the particle settling in the higher elasticity fluid than that in the lower elasticity fluid. The velocity of the fluid in the recirculation region was higher for the flow of the fluid with higher elasticity. The presence of negative wakes having fast moving fluid in the reverse direction near the settling particle possibly creates an additional drag force (acting on the particle in the direction opposite the particle movement), which would eventually slow down the settling particle.

Knowledge of the settling behavior of particles is indispensable to design and optimize numerous industrial operations such as cuttings transport in oil and gas well drilling and proppant transport in hydraulic fracturing. In this study, by conducting experiments under controlled conditions, we were able to show how the change in fluid elasticity influenced the particle settling velocity. The results from this fundamental study can be used for development of optimum drilling and fracturing fluid formulations for effective transport of cuttings and proppants.

Commentary by Dr. Valentin Fuster
2018;():V008T11A054. doi:10.1115/OMAE2018-77386.

The objective of drilling a well is to prepare a clean hole without obstructions for further casing and production tubing running. Cuttings transport has always been important, but challenging process, especially when drilling long directional wells. Poor hole cleaning causes severe problems, as stuck pipe, extreme torque and drag, difficulties in casing landing, cementing, etc. Extensive studies of cuttings transport, both theoretical and experimental, have been performed to estimate, for example, cuttings concentration and cuttings slip velocity to determine optimal conditions for effective hole cleaning.

This paper presents a dynamic analysis of cuttings transport in non-Newtonian fluids based on a transient drift-flux model and an associated numerical scheme AUSMV (advection upstream splitting method) developed by Evje and Fjelde 2002. In this paper, the scheme is modified to simulate cuttings transport dynamically taking into account effects related to pressure, temperature and cuttings slip.

During drilling, the heat is transported from the formation into the wellbore and up to the surface. In this paper, the energy balance is enhanced by introducing an analytical temperature model into the AUSMV scheme. The temperature distribution along the well is calculated at the beginning of simulation and kept constant throughout the simulation.

Additionally, the AUSMV scheme is improved by considering drilling fluid’s transport- and thermal properties. Transport properties of an oil-based mud, such as viscosity and density, are obtained from experiments. The experimental results were used to determine the coefficients in a linear density model used in the study to investigate the effect of non-Newtonian behavior on the heat transfer, cuttings transport and downhole pressure. Furthermore, a model to calculate the apparent viscosity at various pressures and temperatures was developed based on the experimental results and used to evaluate the impact of viscous forces on the cuttings distribution in the well.

Presented numerical scheme solves dynamic cuttings transport problems taking into account the slip velocity variation with wellbore geometry, operational (controllable) parameters and formation properties. In comparison to the traditional steady-state models, the transient cuttings transport model with integrated depth-dependent parameters gives a possibility to achieve a more realistic simulation of cuttings transport, distribution and accumulation along the wellbore through the time.

Commentary by Dr. Valentin Fuster
2018;():V008T11A055. doi:10.1115/OMAE2018-77515.

Primary cementing is a critical well construction operation that should ensure annular zonal isolation over the life cycle of the oil well. Efficient conditioning and mobilisation of mud prior to cementing is important to ensure that residual mud, especially in washout zones, does not contaminate the cement slurry. Therefore, experiments are carried out to better understand the flow dynamics and associated phenomenon in irregular geometry.

The narrow annulus between casing and formation is approximated by a rectangular slot, in order to aid instrumentation and data acquisition purposes. This methodology can be justified to reproduce flow in narrow annuli fairly well, and is considered a very useful technique for measurement in narrow geometries.

Particle image velocimetry (PIV) is used to obtain the liquid velocity profiles in regular and irregular sections of the experimental setup. Analysis of velocity profiles and vector fields provides information on regions of flow in the vicinity of the irregularity, and this allows a systematic study on the effects of flow rate in regular and irregular wellbore geometries. Entry effects from regular to irregular section and the development of areas with recirculation zones are investigated in irregular section. This enables us to estimate variability of circulation efficiencies in the irregularity. The experimental results are compared with numerical simulations in corresponding irregular geometry.

Commentary by Dr. Valentin Fuster
2018;():V008T11A056. doi:10.1115/OMAE2018-77519.

Primary cementing is an important well construction process that should establish well control barriers and zonal isolation. Critical for primary cementing is the successful displacement of drilling fluid from the annulus between casing and formation by a sequence of spacer fluids and cement slurry. Failure to displace the drilling fluid may compromise the annular cement integrity and result in contaminated cement with degraded mechanical properties. Issues such as eccentricity, washouts and other geometric irregularities in the wellbore can complicate the displacement processes, and their effect on the quality of the cementing job and the final result is linked to uncertainty.

We present numerical simulations of the displacement process between two viscoplastic fluids in the vicinity of a symmetric local hole enlargement. The study is limited to laminar flow regimes in the regular part of the annulus, and we focus on a near-horizontal section with significant eccentricity and small annular clearance. We vary the volumetric flow rate and the mass density difference between the fluids, and study how the irregularity affects the displacement efficiency and the presence of residual fluid in and after the irregularity.

In the regular part of the geometry, eccentricity favors flow in the wider, upper part of the annulus, while density difference leads to azimuthal flow from the top to the low side of the annulus. The results support the assumption that increasing the mass density difference improves the displacement efficiency. In the laminar regime, lower flow rates can be favorable over higher ones in terms of efficiency measured as a function of volume that is pumped into the enlarged section.

Displacement of drilling fluids for primary cementing is a rich flow problem involving different non-Newtonian fluids and possibly irregular geometry. Simulations of the displacement process can aid in optimizing fluid properties and injection rates for primary cementing operations, and assist cement log interpretation after the operation.

Commentary by Dr. Valentin Fuster
2018;():V008T11A057. doi:10.1115/OMAE2018-77547.

Gas kicks can occur during conventional drilling operations, in which case the well has to be shut in and the kick circulated safely out of the system. In back pressure managed pressure drilling (MPD) systems, one can tolerate minor influx sizes before the well is shut in.

However, when using oil based mud, solubility issues can complicate the picture making both kick detection and safe handling of kicks more complex. For sufficient large pressures the solubility can be infinite. A kick can also be taken undetected and reach the riser before the free gas suddenly emerge with a corresponding volume expansion that can unload the riser. Managed pressure drilling can be based on having a rotary control device on top of the riser, which makes it possible to add a backpressure on top to dampen the volume expansion, but possibly also change the depth where free gas emerges. It has been shown in another paper how one can use transient models to predict what kind of surface pressure is needed to maintain a constant bottomhole pressure when free gas emerge.

In this paper, a fully transient model developed for a research cooperation between a research institute and Academia will be presented. The model includes behavior of kicks in oil based mud and solubility issues. The model will be used to study the behavior of kicks in riser when considering a backpressure MPD system with special focus on MPD from floaters. One objective will be to show how the results can be impacted by accuracy in the calculation method due to the amount of numerical diffusion present. Another objective will be to show how the PVT model adopted can affect the results. In addition, one will study the impact on results when varying physical input parameters like kick size, magnitude of pore pressure and the geometry of the riser.

Commentary by Dr. Valentin Fuster
2018;():V008T11A058. doi:10.1115/OMAE2018-77614.

Drilling fluids experience a wide range of shear rates and oscillatory motion while circulating through the well and also during the operations for solids control. Therefore, it is important to investigate the influence of oscillatory fields on the velocity profiles, shear rate and resulting rheological condition of non-Newtonian polymers, which are additives in drilling fluids. In this paper, we present the dynamic velocity profiles within both Newtonian (deionized water) and non-Newtonian liquids (Polyanionic Cellulose – PAC) exposed to oscillatory motion. A 15 cm × 15 cm square cross-sectional liquid column was oscillated horizontally with very low frequencies (0.75–1.75 Hz) using a laboratory made oscillating table. The dynamic velocity profiles at the bulk of the oscillating liquid column were visualized by the Particle Image Velocimetry (PIV) method, where the motion of fluid is optically visualized using light scattering “seeding” particles. Increased frequency of oscillations lead to different dynamic patterns and ranges of velocity-shear magnitudes. The experiments are part of a comprehensive study aimed at investigating the influence of low frequency oscillations on particle settling in non-Newtonian drilling fluids. It is discussed, how such motion imposed on polymeric liquids influences both flow dynamics as well as local settling velocities of cuttings particles.

Topics: Fluids , Drilling
Commentary by Dr. Valentin Fuster
2018;():V008T11A059. doi:10.1115/OMAE2018-77615.

Preflushes are often used as part of the sequence of fluids pumped in primary cementing. Usually two functions are served by preflushes: I) to wash the drilling fluid ahead, by a combination of turbulence and chemical reaction; II) to provide a chemically compatible spacer between the lead slurry and the drilling mud. In some cases a wash precedes a spacer, but often only a single preflush is used. We consider well parameters typical of surface casing cementing in North Eastern British Columbia. Using a two-dimensional model of annular displacement flows, we show that the wash concept is flawed. In particular, in a sequence of simulations varying from intermediate density to low density we show that the wash progressively advances ahead of the lead slurry, channeling rapidly up the wide side of the annulus. Even when fully turbulent, it is ineffective at displacing mud from around the annulus, invalidating the motivation of chemical cleaning through contact time. Furthermore, the advance along the wide side of the annulus drains the volume of fluid separating the cement from drilling mud. Thus, the idea that the wash provides a barrier between slurry and and mud is invalid.

Commentary by Dr. Valentin Fuster
2018;():V008T11A060. doi:10.1115/OMAE2018-77630.

One current methodology for Carbon Capture and Storage (CCS) involves pumping carbon dioxide (CO2) into a depleted oil and gas reservoir, usually via an existing well. Permanence of the storage in this case relies on the integrity of the reservoir and also the avoidance of leakage at the points of entry. Two different cementing procedures are involved in the latter problem: primary cementing and squeeze cementing. Here we consider how to track the interface between two fluids during primary cementing. The main idea is to exploit the density difference between successive fluids pumped in order to design a tracer particle to sit at the interface. Although apparently trivial, such particles must also overcome strong secondary flows in order to remain in the interface. We provide a proof of concept analysis of this situation assuming the displacement involves laminar flows of two Newtonian fluids in a narrow vertical annulus and demonstrate its feasibility.

Commentary by Dr. Valentin Fuster
2018;():V008T11A061. doi:10.1115/OMAE2018-77656.

A new 1D dynamic model was developed to predict the liquid-particle flow behavior in a horizontal pipe. The dynamic model combines three effects: steady-state solutions, the Bernoulli effect (due to local accelerations), as well as the flow separation and re-circulation zone occurring at the lee-side of a dune. Experiments of liquid-particle flow were conducted in a medium-scale flow loop, and the results were compared with the dynamic model. Two high-speed cameras were used to measure the particle dune characteristics, mainly length and height of the dune, as well as the particles velocity. Particles were spherical glass beads with median diameter of 0.3 and 1.2 mm. Water was used as test fluid, and the flow was fully turbulent. It was found that the model captured the essential physics of particle transport for the measurements reported, such as prediction of pressure drop fluctuations, as a function of both space and time.

Commentary by Dr. Valentin Fuster
2018;():V008T11A062. doi:10.1115/OMAE2018-77662.

In this paper both a coarse and fine wood fibre type of Lost Circulation Material (LCM) is tested in the laboratory. It is shown how these fibre treatments work. The fibre type is partially oil wetting making them suitable for application in oil based drilling fluids. The fine material helps stopping small drilling induced fractures, while the coarse helps stopping lost circulation into several natural fractures or coal or conglomerate formations. In the article, the selection of wood fibres is described in more detail.

Testing of the fine materials were conducted conventionally by pumping drilling fluid volumes with LCM onto slotted disks in fluid loss apparatuses. The coarse fibres are too large to be tested in these apparatuses. Therefore, gravel with grain diameter around two centimetres was filled into transparent cylinders. The pore throats created by these gravel particles were above half a centimetre. For both of these LCMs the experiments show the sensitivity of the LCM concentration in the drilling fluid to stop the lost circulation. Also, it is shown the effect of the LCM on viscous properties of the drilling fluids. Not all LCMs can be pumped through the bit. The article describes the need for circulation subs in the bottom hole assembly (BHA) to hinder the LCM blocking the entire BHA.

Topics: Fibers , Wood products
Commentary by Dr. Valentin Fuster
2018;():V008T11A063. doi:10.1115/OMAE2018-77719.

Pushing the boundaries of oil and gas exploration and development to new frontiers have led to exposure and more significant uncertainties, which necessitates robust strategies and techniques. With the increasing water depth, longer risers, and harsh pressure and temperature conditions; the risk of riser gas getting undetected get bigger. The lack of an integrated system to anticipate the controlling parameters at the choke below the BOP constrains the tackling operations and exacerbate the side effects of oil and gas well blowouts. This leads to an urgent need for an extensive study to address the riser gas unloading (RGU) events.

This study encompasses the development of a robust model that can characterize the effect of different parameters such as temperature, mud types, back pressure, and solubility in RGU events. It also presents comparative results of oil-based and water-based mud systems, using a novel tool based on analytical and numerical models. The analytical model is constructed using combined gas law, heat transfer mechanism, and gas solubility and bubble point pressure concepts.

Results suggest that the oil-based mud (OBM) takes more time for gas unloading in comparison to the water-based mud. Also, a significant deviation was observed in unloading patterns while considering temperature effect. For the drilling fluid without temperature consideration, the gas unloading occur in a smaller span of time and at a higher depth. Overall, this paper will demonstrate the effect of different parameters affecting the gas unloading in the riser, and present a comparative study of different parameters using an analytical which can be used in the field to get an idea of gas prior to any response for abnormality.

Commentary by Dr. Valentin Fuster
2018;():V008T11A064. doi:10.1115/OMAE2018-77800.

In drilling operations, the downhole pressure (BHP) requires to be closely monitored and precisely managed to avoid potential drilling events harmful to personnel and environment. If the BHP is lower than the pore pressure, kick (amount of influx) from formation will enter the wellbore, which might result in (underground) blowout. If not properly managed, this could be more costly than surface blowouts [1]. Well control aims to stop and remove the influx and re-establish primary barriers.

Managed Pressure Drilling (MPD) is an advanced drilling technology capable of precisely controlling annular pressure profile throughout the wellbore. In this study, a high fidelity transient flow model is used for simulating dynamic well control procedure in MPD to properly manage annular pressure during kick circulation after the kick is detected. In this work, an automated well control in MPD is simulated, where PID control algorithm is implemented by manipulating choke valve opening to dynamically regulate the BHP during kick circulation. The main aim is to investigate dynamic kick management with the use of different type of muds, water based mud (WBM) and oil based mud (OBM). For different mud systems, the well control performances for long extended reach wells are evaluated and compared. From simulations, it shows that the OBM is able to hide the influx to a large extent, than the WBM due to the much higher gas solubility of the OBM. In HPHT wells, the OBM is superior to the WBM with proper automatic surface pressure control in MPD operations. Using complicated dynamic flow model can provide more precisely surface pressure control for realtime dynamic kick management.

Topics: Pressure , Wells , Drilling
Commentary by Dr. Valentin Fuster
2018;():V008T11A065. doi:10.1115/OMAE2018-77832.

A drilling fluid for drilling deviated wellbores must provide adequate hole cleaning efficiency for all well angles relevant to the operation. For angles near vertical, experience show that hole cleaning is straight forward. In wellbore angles larger than, say, 45 degrees hole cleaning is more difficult. Cuttings beds are formed and at some well angles these beds may avalanche during circulation stops etc.

This paper presents results from laboratory tests with injected cuttings using a low viscosity oil based drilling fluid with micronized grained barite as weight material. The fluid is designed for highly deviated wells with low ECD requirements and the cuttings transport performance through relevant wellbore inclinations was investigated.

The experiments have been performed under realistic conditions. The flow loop includes a 10 meters long test section with 2” OD freely rotating steel drill string inside a 4” ID wellbore made of steel, representing a cased wellbore. Sand particles were injected while circulating the drilling fluid through the test section. Experiments were performed in three wellbore inclinations: 48, 60 and 90 degrees from vertical.

Results show that hole cleaning in absence of drill pipe rotation is significantly improved if the well angle is less than a critical angle. This critical angle appears to be less than 60 degrees from vertical. Further result show that this critical inclination angle is dependent to the drill string rotation rate and the annular flow velocity.

Topics: Wells
Commentary by Dr. Valentin Fuster
2018;():V008T11A066. doi:10.1115/OMAE2018-78149.

Conventional clay-based drilling fluids often experienced difficulties in controlling the rheological properties, gelation, and filtration due to flocculation of clay at the temperature higher than 121°C. Deflocculant or thinner, one of the drilling fluid additives, serves a significant role in preventing the association of clay particles particularly in high temperature environments such as high-pressure and high-temperature (HPHT) deep-water drilling. Lignosulfonate has been commonly used in the industry as deflocculant for clay-based drilling fluids since the late 1950s as a replacement for Quebracho tannin. Degradation at the elevated temperature limits the usage of anionic polymer and lignosulfonate. In improving the stability of deflocculant at high temperature, lignosulfonate is admixed or reacted with chromium and iron compound to obtain ferro-chrome lignosulfonate whose temperature limit is approximately 190°C. While recent ferro-chrome lignosulfonate contains less chrome than in the past, development of more environmentally friendly and higher thermally stable deflocculant is still needed. In HPHT environment which requires high-density drilling fluid, a higher thermally-stable deflocculant is also valuable for barite sagging that becomes problematic at a temperature higher than 200°C.

Several findings in the past development of adhesives show that addition of tannin improves the thermal stability of lignosulfonate. Tannin is a polyphenolic compound that is natural, non-toxic and biodegradable and can be found in various part of a vascular plant other than Quebracho. Lignosulfonate, on the other hand, is a byproduct of the paper pulping process. Tannin and lignosulfonate are cross-linked to obtain tannin–lignosulfonate for use as a high-temperature drilling fluid deflocculant. Tannin and lignin are the most abundant compounds extracted from biomass. The wide availability of tannin and lignosulfonate is an advantage from a manufacturing cost viewpoint.

In this paper, an overview of drilling fluids, classification of drilling fluid, high temperature reservoir environment, and mechanisms of dispersion and deflocculation are presented. Further discussion on the potential development of eco-friendly tannin–lignosulfonate based drilling fluid system for the high temperature well development also presented.

Commentary by Dr. Valentin Fuster
2018;():V008T11A067. doi:10.1115/OMAE2018-78518.

For deepwater oil and gas well drilling with the issue of highly mineralized formation brines, it is required that the drilling fluid properties are not affected by the high salinity formation fluid and the low-temperature environment. A novel drilling fluid mainly consists of fuzzy-ball fluid, which has an excellent tolerance to salinity and low temperature, has the potential to be applied for deepwater drilling to achieve safe and efficient drilling tasks.

Experimental studies and field tests have been carried out to characterize the rheological properties of fuzzy-ball drilling fluid under different conditions of brine salinity and test temperature. In the experimental test, fuzzy-ball fluids with different densities are prepared with brines of varying salinity mineralized by Ca2+ and Mg2+. The rheological curves are plotted from different apparent viscosities and shear stresses under different shear rates measured by a rheometer under 10 ∼ 80°C and a six-speed viscometer at 0°C.

The results positively showed that the yield stress of fuzzy-ball fluid is stable at a relatively high value with the variation of fluid salinity and temperature. The apparent viscosity slightly increases with the decrease of salinity and temperature. It can be claimed that the rheological properties of fuzzy-ball drilling fluid are stable within the range of salinity and temperature investigated experimentally.

Field tests have been conducted during several workover jobs, the rheological properties of fuzzy-ball drilling fluid were stable at temperatures and salinities on site. Thus, it can be proved that the novel fuzzy-ball drilling fluid could be applied in deepwater drilling under the high salinity formation fluid and low-temperature environment.

Commentary by Dr. Valentin Fuster
2018;():V008T11A068. doi:10.1115/OMAE2018-78695.

When a drilling fluid column remains static over a timeframe of several years, the drilling fluid separates into different sediment phases due to gravity separation. These heavy sediments, entitled “settled barite”, are the cause of significant operational problems several years after drilling.

An important problem caused by settled barite occurs when performing casing cut-and-pull operations during slot recovery and well abandonment: the casing is “stuck” due to the sediments in the annulus outside the casing. The consistency and rheological properties of the sediments determine how easily the casing is removed.

In this paper, we report a preliminary study were we have artificially prepared gravity sediment phases for two different types of water-based drilling fluids; one KCl/polymer-based fluid and one bentonite-based fluid. By studying the rheological properties of the obtained sediment phases, we see that there are considerable differences between the sediments for these different drilling fluids.

Commentary by Dr. Valentin Fuster
2018;():V008T11A069. doi:10.1115/OMAE2018-78702.

In recent years, the application of nanomaterial has been attracting the oil and gas industry. Nanomaterials research results show an improving performance of cement, drilling fluid and enhanced oil recovery.

In this paper, the effect of multi-walled carbon nanotube (MWCNT) and MWCNT functionalized with ligands–OH and - COOH nanoparticles on laboratory drilling fluids formulated from bentonite, KCL, Carboxymethyl cellulose (CMC) and xanthan gum (XG) was studied. The formulations and tests were performed at room temperature.

The results show that addition of 0.0095wt.% of MWCNT, MWCNT-OH and MWCNT-COOH nanoparticles in CMC/bentonite system decreases the filtrate-loss by 8.6 %, 7.1 % and 17.9 % respectively. These particles also decreased the coefficient of friction by 34 %, 37 % and 33 % respectively. In xanthan gum drilling fluid, 0.019wt%. MWCNT reduced the friction coefficient by 38 %.

Commentary by Dr. Valentin Fuster

Petroleum Technology: Well Plugging and Abandonment

2018;():V008T11A070. doi:10.1115/OMAE2018-77875.

Through the life-time of a production field in the offshore petroleum industry it is normal to drill several new wells for both production and injection purposes. The initial well template, either at the platform or at a subsea installation, has space for a fixed total number of wells. When this limit is reached an old well needs to be plugged and the well slot reused to allow new wells to be drilled.

In order to re-use well slots and benefit from full diameter when constructing the new well, it is required to remove the tubulars in the upper part of the plugged well. The outside of these tubulars are normally in contact with cement or settled particles from shut-in drilling fluids. Removing the tubular through the cement or settled particle is always challenging and there is need for using new techniques.

In order to address the dominating effects in these operations, down-scaled laboratory tests are performed. The experiments reported here are performed by pulling steel pipes out of a cemented annulus. The pipes used in the tests are down-scaled from typical casing sizes. They are either normal pipes, grooved pipes or pipes with and without collars. Two setups with different geometries are used. The first is selected to study the de-bonding effect from the cemented annulus and the mechanical friction that must be overcome to remove the pipe. The other setup is designed to show the effect of collars when pulling out the tubulars. Since most tubulars in wells have collars between each stand with extended diameter, this effect is important to consider when comparing laboratory results to field operations.

Results show that the loosening force (de-bonding) and pulling force can be significantly reduced by manipulating the pipes with grooves prior to pulling them out. Further, the results show that the most significant resistance when pulling the tubulars are caused by the collars outside the pipe. It is also observed that the effect of collar is significantly reduced when the pipe is grooved between the collars. In total these results provide improved understanding on the dominating effects when pulling pipes from packed wellbore annulus.

Commentary by Dr. Valentin Fuster
2018;():V008T11A071. doi:10.1115/OMAE2018-78347.

A recurring issue in the petroleum industry is the performance of cement in relation to its primary role of providing zonal isolation. Enhanced understanding of this subject offers the possibility to improve the planning and design of the cementing job to minimizing the risk of poor bonding of cement and loss of well integrity. The design and execution of the cement job is by no means an easy task, mainly due to the complexity of the material and process, and the variety in conditions one can encounter downhole. Thus, screening of different materials and conditions is necessary to optimize the success of a cement operation.

This work focused on experimentally testing cement plugs to be able to understand the sealing ability of cement to a casing at relevant temperatures and pressures. A built-for-purpose test setup was designed and assembled, and the goal of this work was to test this new setup and to establish a proper baseline for future test on various cement systems.

The setup consists of a test cell containing the cement plug, an automated pressure regulator used for generating a pressure differential across the cement plug and flow meters to measure the flow rate through the cement plug. The output data from the tests is the differential pressure needed to have breakthrough of gas, and the connection between the flow rate and differential pressure across the cement plug. The possible manipulated variables for the test setup is the cement type and casing surface properties.

Commentary by Dr. Valentin Fuster
2018;():V008T11A072. doi:10.1115/OMAE2018-78532.

Permanent Plug and Abandon (PP&A) operations of the existing production and exploration wells continue to have a higher focus in drilling and well operations for Oil & Gas Companies. It is expected that they will play an important role in the future, and their further optimization and simplification is even more important. This paper describes a successful approach and execution of a challenging Permanent Plug and Abandon operation of a subsea well in the Norwegian Sea by Statoil.

A subsea well at over 350 m water depth was being drilled, when a casing running tool was stuck at the subsea wellhead when running an intermediate casing string. This led to a temporary well abandonment, before permanent P&A operations could be resumed at a later stage. Several concepts and contingency scenarios were evaluated and risk assessed in the planning phase, which required implementation of nonstandard and innovative P&A solutions and equipment. They were developed in the planning phase and reviewed with planning and execution teams, and tested before the operational start-up. Main P&A operational goals were established in the planning phase, and successfully implemented during the operations: 1) well control — confirm there is no gas and no well control risk in the well before resuming P&A operations, 2) gain access to the well by retrieving stuck tool from subsea wellhead, and 3) establish permanent P&A barriers in the well.

Both planning and execution of this operation is described in this paper, which includes main planned operations, and also a strategical approach with several contingency scenarios prepared in order to be able to P&A this well permanently.

Commentary by Dr. Valentin Fuster
2018;():V008T11A073. doi:10.1115/OMAE2018-78749.

Well sections that have been completed with an open annulus between the casing and the rock are occasionally found to be sealed by shale that creeps in and closes the annulus. This process usually happens spontaneously, without deliberate actions from the operator, in weak rocks with high shale content. The phenomenon has been studied in a series of laboratory tests. The tests reveal that annulus pressure may play a significant role in the formation of a shale barrier. The study also shows that formation of the barrier implies damage and permanent deformation of the rock in a limited region around the hole. In the field, a shale barrier is hidden behind the casing and is not directly accessible. They are usually detected by sonic logging tools and verified by pressure communication tests. Interpretation of sonic signals from behind the casing is however challenging, and identification of shale barriers in the field is not trivial.

Commentary by Dr. Valentin Fuster

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