Two-Phase Injection Resurgence Demonstrated in Depleted Well's 4 1/8-inch Openhole Section in Mexico.

Abstract Depleted reservoirs in the southeast region of Mexico have provided an opportunity to revisit underbalanced technology through the application of a two-phase injection in a drilled S-type well, due to the well’s suspect pore pressure gradient reaching as low as 0.54 gr/cc. The operation had considerable risks and required detailed planning, flawless execution, and operational excellence in order for the well to be successfully drilled. The primary objective of the operation was to drill to the Late Jurassic/Kimmeridgian age of the formation at 7680 meters. According to correlated wells, severe losses were expected at the beginning of the top Jurassic age. To address these challenges, a fully automated managed pressure drilling (MPD) system and an 80-cubic-meter-per-minute nitrogen generation and injection system were deployed. These technologies were applied to minimize fluid loss ratios and reduce non-productive time (NPT). The 4 ⅛-inch drilling phase started with a packed bottomhole assembly (BHA) and a 0.95-SG mud weight monophasic system, with the drilling shoe at 6521 meters transitioning to biphasic MPD at 6547 meters because of a severe fluid loss of 22 cubic meters. The drilling operations concluded ahead of schedule, with the successful drilling of 937 meters of open hole. The final total depth (TD) was 7457 meters. This achievement included establishing tripping (speed) records and maintaining minimal fluid losses during the well energizing procedure and drilling operations. The Multiphase Drilling team utilized specialized software for multiphase operations and provided a precise formation pressure characterization, thus facilitating the successful restoration of circulation. This article presents the comprehensive planning process, the effectiveness of the biphasic MPD strategy, and key events that highlight how the fully automated system effectively addressed the challenges posed by drilling in a depleted reservoir.