Geomechanics Study and Laboratory Testing for Time-Dependent Borehole Analysis in Cisubuh Formation, Well ABC-025, Indonesia

Summary Drilling activities in Field X, Northern West Java Basin, exposed geomechanical hazards in the Cisubuh Formation, such as sloughing shale and Tight Hole, leading to drill pipe sticking and increased operational time and costs. In well ABC-022, sloughing shale and overpull events during pipe pulling caused stuck pipes and required a sidetrack. Similarly, in well ABC-020, spot cavings at 1398 mMD during a 12.25” hole short trip led to pipe sticking, requiring tension adjustments and an increase in mud weight from 1.4 to 1.49 SG, adding 13 hours of non-productive time (NPT). To address these issues, an advanced geomechanics study using real-time data was conducted on well ABC-025. Laboratory tests like XRD analysis, triaxial tests, and time-dependent analysis were performed to assess borehole stability. Regional geological analysis revealed the stress regime in Field X, influenced by the Cimandiri-Lembang-Palimanan fault system. Test results showed 6% smectite content, making the shale reactive. 1D geomechanical modeling indicated a collapse pressure of 1.47 SG, recommending a safe mud weight of 1.50 SG. Time-dependent analysis showed that borehole narrowing could occur after five days. The study provided recommendations for new casing and mud designs to mitigate sloughing shale hazards and improve drilling efficiency