Stress Field Delineation using Well Log Data – A Case Study

Abstract

The essentiality of stress field delineation in the subsurface arises in several contexts like well planning and monitoring to ensure safe drilling of a borehole. Work reported here concerns with methodology developed for delineating stress fields in rock strata using log data which includes crossed dipole and monopole acoustic data acquired in boreholes. Orientation of the principal stresses in the horizontal plane has been arrived at by computing relative azimuth of maximum and minimum stress directions with respect to a designated dipole transmitter’s axial orientation. Static Poisson Ratio and Static Young’s modulus have been computed using customized relationships with due care has been taken to factor-in fluid effects where compressible fluids are known to present within pore space of the rock. Stresses magnitudes and UCS model have been subjected to a validity check through prediction versus actual of presence / absence of breakouts (the latter from image data evidence) and the match is very good.