Geomechanics-Aided Successful Execution of a Challenging Build-Up Section Through Mixed Lithologies

Abstract

Abstract This study presents an example of geomechanics-aided successful delivery of a challenging 4100 ft long build-up section through mixed lithologies, towards minimum horizontal stress direction. The primary challenge in the build-up sections of the studied offshore exploration field in the Middle East was the mechanical instabilities of the weak shales which contributed to extensive tighthole, pack-off, backreaming, and therefore significant non-productive times. Other associated challenges were the differential sticking tendencies in the porous sandstone layers, and partial to total loss risks within the carbonates. The optimization roadmap comprised adequate mud weight design by geomechanical modeling in the planning phase, and real-time geomechanics advisory in the execution phase. The in-depth analyses of offset wells provided critical insights regarding the commonly occurring and potential drilling hazards across various formations. The post-drill geomechanical modeling and wellbore stability analysis of offset wells, calibrated with drilling events-based observations provided a clear understanding of the collapse pressure behavior of various formations. Based on the geomechanical modeling, a safe mud weight window as well as the minimum required mud weight were recommended to tackle mechanical instabilities. Real-time monitoring of the LWD data, aided by right-time geomechanical advisory support ensured successful well delivery. The drilling and the final BHA pull-out were completed without any mechanical instability issues which annulled the requirement of consecutive reaming trips, saving additional rig days. Successful completion of the challenging build-up section parallel to the Shmin azimuth registered zero NPT with notably improved drilling performance.