Learnings from Strain Measurements on an In-Field Conductor and Wellhead System – Rohit Shankaran, Principal Engineer, London

21st June 2018 – Structure, Safety and Reliability Symposia in the 2-6 Session 1 Well Integrity and Reliability Assessment from 13:30 to 15:00.

Madrid Marriot Auditorium and Conference Center, Madrid, Spain

In recent years due to use of drilling risers with larger and heavier BOP/LMRP stacks, fatigue loading on subsea wellheads has increased, which poses potential restrictions on the duration of drilling operations. In order to track wellhead and conductor fatigue consumption to support safe drilling operations a range of methods have been applied:

  • Analytical riser model and measured environment;
  • BOP motion measurement and transfer function;
  • Strain gauge data.

Strain gauge monitoring is considered the most accurate method for measuring fatigue consumption. To compare the three approaches and establish recommendations for an optimal approach and method to establish fatigue accumulation of the wellhead, a monitoring data set is obtained on a well offshore West of Shetland. This paper presents an analysis of measured strain, motions and analytical predictions with the objective of better understanding the accuracy, limitations, or conservatism in each of the three methods defined above.

Of the various parameters that affect the accuracy of the fatigue damage estimates, the paper identifies that the selection of analytical conductor-soil model is critical to narrowing the gap between fatigue life predictions from the different approaches. The work presented here presents the influence of alternative approaches to model conductor-soil interaction than the traditionally used API soil model.

Overall, the paper presents the monitoring equipment and analytical methodology to advance the accuracy of wellhead fatigue damage measurements.