Understanding Torque and Drag: Best Practices and Lessons Learnt from the CaptainField's Extended Reach Wells

摘要

This paper describes how torque and drag (T&D) analysis wasused to successfully drill extended reach (ERD) wells in theCaptain field in the North Sea. The issues and best practicesassociated with using this basic real-time drilling technique,particularly on Captain subsea development wells drilled from2000 to 2003, are explained. The paper also explains thetactics used in overcoming issues such as how far could wedrill and the associated risk. The applicability of availableT&D reduction technologies and why many of them wereeliminated as possible solutions reinforced the criticality ofgood T&D analysis on this project.The Captain subsea wells have the highest aspect ratio(unwrapped displacement [UD] / true vertical depth [TVD])ever for development wells drilled and completed from afloating vessel. Although the wells are short in displacementfor ERD wells, the shallow nature of the reservoir requires theapplication of T&D analysis, which has been at the core ofgood ERD drilling principles and practices for some time.This paper outlines what T&D analysis is and why it isimportant. The design of the bottomhole assembly (BHA) anddrilling string, drilling string buckling, friction factor (FF)analysis, casing sanding considerations, trajectory design, andwellbore tortuosity all must be considered in applying thisbasic technique to field operations. Other issues such as why itis often misunderstood or badly applied, the importance ofcalibration with offset data, and conditions that effect FFdetermination are explained.