Assurance of wellbore stability (WBS) is of utmost concern and a key challenge in drilling an inclined well in ultra deep water of the East Coast of India. The WBS analysis requires accurate modeling of earth stresses and rock mechanical properties. These processes are primarily based on sonic logs (compressional and shear slowness), bulk density and lithological distribution. To understand and address drilling complications in the study area, post-drill (offset well analysis) and real-time drilling geomechanics is carried out in this well.
1D mechanical earth model (MEM) and WBS model is constructed for offset wells, which is calibrated with caliper log, pressure test and leak-off data sets. WBS analysis suggested drilling with lower mud weight in the zones of shear failure and pack-off. Disparity in resistivity values is also observed when wireline logs and Logging-While-Drilling (LWD) logs are analyzed. This might be due to mud invasion or fluid-shale interaction in the open hole, as it is resolved by changing mud system from water based mud (WBM) to synthetic oil base mud (SOBM). The post-drill analysis of offsets wells established parameters for the upcoming inclined well.
The planned well is the first inclined well (horizontal drift more than ~2000m) in ultra deepwater of the East Coast of India to avoid the drilling risks; real-time drilling geomechanics is first time put into operation. Required sonic and density data is received in reasonable time intervals to perform real-time analysis. Timely updates on rock mechanical properties are provided to client, which helped in optimizing drilling parameters. As a result, first inclined well in ultra deep water in the East Coast of India was drilled successfully.