In situ stress state in the petroliferous Barmer Basin, northwestern India: A new geomechanical approach

Limited understanding of state of stress has led to wellbore complications attributing to significant nonproductive time during drilling operations in the Barmer Basin, northwestern India. This paper deals with determination of state of stress in the hydrocarbon-bearing Barmer Basin by incorporating well data, earthquake aftershock data, and structural fieldwork data. Vertical stress (S-v), pore pressure (P-p), and minimum horizontal stress (S-hmin) were estimated from petrophysical logs using the effective stress approach and are calibrated to available pressure and stress measurements. Maximum horizontal stress (S-Hmax) is constrained using frictional faulting theory. A new estimation approach, independent of S-hmin, is presented in the zones where wellbore failures such as borehole breakouts (BOs) and drilling induced tensile fractures (DITFs) occur together. Stress orientation was inferred from wellbore failures (BOs and DITFs) recorded by image logs, shear sense from deformation bands, and stress inversion from aftershock data. The S,, ranges from 0.9 to 1.05 psi/ft, Pp ranges from hydrostatic to 0.65 psi/ft, Shmin ranges from 0.7 to 0.98 psi/ft, and SHmax constrained by the presence of BOs and DITFs ranges from 1.2 to 1.82 psi/ft and 1.24 to 1.85 psi/ft, respectively. The SHmax from the new combined failure approach ranges from 1.09 to 1.82 psi/ft. The SHmax orientation is predominantly north-south and is consistent spatially basin-wide. Finally, the relative comparison of the three principal stresses suggests a strike-slip (S-Hmax > S-v > S-hmin) stress state in the basin and marginally reverse (S-Hmax > S-hmin >= S-v) in the northern part, where transpressional features are evident. The observed present-day strike-slip stress state and principal stress (S-Hmax) orientation is consistent with the stress inversion analysis of Bhuj earthquake aftershock data. Also, based on paleostress analysis of outcropping structural fabrics and kinematic indicators, and understanding of the Indian plate movement and collision tectonics in the Himalayas during the Cenozoic, it is inferred that the area has been under a strike-slip stress state since at least the Oligocene.

Automated summary

This paper determines the state of stress in the Barmer Basin using various data and methods. The results show that the stress state in the basin is predominantly strike-slip, with a north-south orientation.