Integration of Electrical Micro-Image Log, Advance 3D Acoustic Anisotropy and Fracture Stability Analysis – A Complete Solution for Basement Reservoir

Abstract

Owing to the depleting reserves in the conventional reservoirs over the last few years, unconventional reservoirs have gained significant importance in the exploration of oil and gas. Basement rocks, though non-sedimentary in origin, is looked upto as one of the important unconventional reservoirs. Deccan volcanics in Kutch-Saurashtra is one such example from India. This study shows and validates a methodology of how acoustic log data can be integrated with borehole images to understand reservoir properties that governs flow. It has been noticed that presence of open fractures is not the single biggest driver contributing to production. Insitu stress plays a critical role in guiding fracture mobility. To understand and determine which fractures would contribute to flow, a geomechanical study of performing the fracture stability analysis has been carried out. This generates a Mohr circle plot that defines the Mohr-Colomb shear failure criteria using the stress and critical fracture angles. Combining these three-way approaches of acoustic, image log and geomechanics, a workflow has been established for this field to identify fractures and quantify the permeable zones. This workflow has been used for two nearby wells in this field and subsequent result emphasises the utility of this method to find out sweet spots of fluid flow in fractured basement.