Anisotropic Reverse-Time Migration for Imaging Fracture Zones at Eleven-Mile Canyon

Abstract

Fracture zones behave as anisotropic media for seismic-wave propagation. Conventional reverse-time migration (RTM) is based on seismic-wave propagation in isotropic media, and usually fails to reliably image fracture/fault zones for geothermal exploration. We develop a novel anisotropic RTM method for reliable imaging of fracture zones. The method employs an implicit wavefield separation scheme to properly handle arbitrary anisotropy of fracture zones. We validate our new method using synthetic data for a geophysical models of Eleven-Mile Canyon in Nevada containing several fracture zones. The synthetic test results show that our new method produce higher-quality images of fracture zones than the conventional RTM. Several 2D surface seismic reflection datasets were acquired at Eleven-Mile Canyon in Nevada for geothermal exploration. For imaging faults and fracture zones at Eleven-Mile Canyon, we first construct anisotropic elastic models using the acquired seismic data and our multiscale anisotropic waveform inversion algorithm. We then apply our new anisotropic RTM method to the seismic data to image subsurface structures at Eleven-Mile Canyon geothermal exploration site. Our preliminary imaging results of field seismic data demonstrate the effectiveness of our new anisotropic RTM method for imaging fracture zones.