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Reliable, Low Footprint and Cost-Effective Monitoring of Wellhead Loads Using Autonomous IMUs for Fatigue Estimates

[+] Author Affiliations
Kristian Authen, Hallgeir Melbø

4subsea, Hvalstad, Norway

Guttorm Grytøyr

Statoil ASA, Fornebu, Norway

Paper No. OMAE2015-41882, pp. V05BT04A052; 5 pages
  • ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering
  • Volume 5B: Pipeline and Riser Technology
  • St. John’s, Newfoundland, Canada, May 31–June 5, 2015
  • Conference Sponsors: Ocean, Offshore and Arctic Engineering Division
  • ISBN: 978-0-7918-5652-9
  • Copyright © 2015 by ASME


Wellhead systems in the North Sea are frequently subjected to large bending loads, due to shallow waters, heavy seas and semi-submersible drilling rigs. This makes fatigue of wellhead systems a challenge.

The fatigue estimates of such wells are often conservative when based on global FE riser simulations. To reduce the conservatism from such simulations, measurements of the actual wellhead loads have been performed on certain occasions. This is often a costly and intricate process that usually require a subsea cable from the rig. This paper presents an alternative method for measuring WH loads by the use of autonomous motion sensors (IMUs) on the BOP and lower end of the drilling riser.

Measured inclinations from the IMU on the riser are used to capture the loads acting from the riser onto the BOP. The inclinations from the sensor on the BOP are used to capture the dynamic response of the BOP and well system. The combination of the measured excitation load and the measured dynamic behavior, makes it possible to reliably estimate the WH bending moment, without the use of riser simulations.

The accuracy of the proposed methodology is demonstrated in a FE riser simulation. The model acts as a controlled environment where both input parameters and WH loads are known. The sensor data is extracted from the analysis at the relevant locations, run through the proposed methodology and then compared with the WH loads in the model.

As a final verification, the method is tested on data from an actual measurement campaign where both IMU and strain gauge measurements are available. The WH loads will be calculated based on the proposed method and IMU data, and the results will be compared to the data from the strain gauge based load sensors.

Copyright © 2015 by ASME
Topics: Fatigue , Stress



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