Geomechanical characterization of subsurface formations with stress rotation in Assam Gap, Northeast India

Modification of local stress orientation is an interesting issue for fluid migration and seal integrity at the faulted region of Assam Gap holding major oil/gas fields of India. Main objective is to scrutinize the stress pattern at the faulted blocks in this seismic gap. Geomechanical characterization of the study area has been carried out by integrating seismic and well log data through velocity model. A fresh approach adopting inverted post-stack seismic section tied with wells is considered to map the geomechanical parameters and stress magnitudes of the study area. The 3D structural model considers the geomechanical layers delineated by the mapped rock mechanical properties and local faults revealed in post-stack seismic sections. The 3D finite element model proposed in this study allows the computation of stress orientation, constraining deformation at the north facing edge and imposing the regional stress field towards NE-SW direction. The pattern of stress orientation shows the limited variation in stress direction across the geomechanical layers paralleling the regional stress direction of NE-SW. However strong stress rotation amounting about 20 degrees is observed near the fault blocks and scattered rotation ranging from 20 to 90 degrees in the fault plane. The model predicted stress direction is validated with the stress direction at well location from Fullbore Micro resistivity Imager data.