Improved Drilling Performance in a Troublesome Environment

Abstract

Summary This paper describes an example of drilling-hazard mitigation. It demonstrates how a completely fresh approach, involving geomechanical analysis, planning of a new revised well trajectory, and real-time well monitoring, can reduce nonproductive time and cost and mitigate against unplanned terminal events. Recent drilling operations in a mature field in the North Sea were severely disrupted by wellbore deterioration, stuck pipe, and lost-circulation incidents. A complex geological sequence of tilted fault blocks and partially depleted reservoir sands made well-trajectory and wellbore-stability planning difficult. After two unsuccessful sidetrack attempts, an integrated operator/contractor team performed a detailed audit of the drilling problems and built a geomechanical Earth model to evaluate drilling hazards and develop strategies to mitigate any further wellbore instability. Well objectives were re-evaluated, and a new approach to the drilling process was developed. The keywas simplification of the well path. The operational solution featured management of drilling hazards through a real-time risk-mitigation process. Additional engineers at the well site managed drilling parameters; continuously monitored cavings, cuttings, and drill fluids; and analyzed drilling mechanics and logging-while-drilling (LWD) log data for indications of impending problems. A Web-based real-time data-transfer system was used to deliver data to the onshore drilling and subsurface teams. These methods, combined with advanced communication techniques, enabled tight control of drilling parameters and trajectory and enhanced collaborative understanding within the multidisciplinary team. The third sidetrack was completed without incident, within time, and under budget.