Performance Evaluation of Recently Developed Soil Models in Well Conductor Fatigue Analysis using Field Measurements

Abstract

Abstract American Petroleum Institute (API) [2] recommendations for modeling the lateral soil resistance-displacement (p-y) response were not developed for fatigue analysis of deepwater wells. The recently developed soil models [1] is aimed to fill this knowledge gap. Based on extensive physical testing in a geotechnical centrifuge and complementary numerical modelling, a more accurate approach was developed for soil modeling specific to well conductor fatigue analysis. The approach was presented at OTC2015 [1]. While the approach proposed in [1] performed very well in predicting the fatigue damage in the model tests, its performance is yet to be evaluated against actual field data obtained in the field. This paper evaluates the performance of the recently developed soil models in predicting field measurements and fatigue damage obtained from a monitored well in the Gulf of Mexico (GoM). Important considerations for modeling soil response (e.g., modeling of soil crust near mudline) are also discussed. The new approaches are applicable to fatigue analysis of conductors pertaining to subsea wells worldwide. The motion monitoring loggers collect acceleration and angular rate information at the point of installation. The objective was to investigate the fatigue performance of the wellhead and conductor system. Fatigue was estimated based on the motion data collected from the data loggers. The measured motions and fatigue damage obtained from the loggers were compared to those estimated from predictive methods using the proposed soil model. This paper demonstrates that the recently developed soil models perform satisfactorily in predicting the deformations (displacements and rotations) measured at the top of the lower marine riser package (LMRP); hence, providing a more accurate prediction of the system (LMRP, wellhead and casings) response and thereby, its fatigue damage.