Three Dimensional Stress Field Estimation Using S-Wave Anisotropy Obtained from Ambient Noise Records of Vertical Seismic Array System

Abstract

Abstract In this study, we propose a new approach to estimate depth-dependent stress field in a borehole instead of conventional in-situ measurement methods. Seismic interferometry and Alford rotation methods are used to obtain S-wave anisotropy as a proxy of stress field. Ambient noise records observed by horizontal components of vertical seismic array system installed in a borehole were used as input data. We first calculate virtual cross dipole seismic records by seismic interferometry method applied to the observed continuous ambient noise records. Then we applied the Alford rotation and layer stripping technique to obtain depth-dependent S-wave anisotropy parameters, i.e., the orientation of fast S-wave and the difference between fast and slow S-wave velocities of formations along the vertical axis of a borehole. Obtained results, the orientation of fast S-wave, have very good agreement with directions of principal horizontal stress, which was revealed in the analysis of borehole breakout just after drilling the borehole. We propose that our approach would readily be applied to monitor the stress field around a borehole instead of conventional in-situ measurement methods.