PS energy imaging condition for microseismic data — Part 1: Theory and applications in 3D isotropic media

Abstract

Accurately estimating event locations is of significant importance in microseismic investigations because this information greatly contributes to the overall success of hydraulic-fracturing monitoring programs. Full-wavefield time-reverse imaging (TRI) using one or more wave-equation imaging conditions offers an effective methodology for locating surface-recorded microseismic events. Although, to be most beneficial in microseismic monitoring programs, the TRI procedure requires using accurate subsurface models that account for elastic media effects. We have developed a novel microseismic (extended) PS energy imaging condition that explicitly incorporates the stiffness tensor and exhibits heightened sensitivity to isotropic elastic model perturbations compared with existing imaging conditions. Numerical experiments demonstrate the sensitivity of the microseismic TRI results to perturbations in P- and S-wave velocity models. Zero-lag and extended microseismic source images computed at selected subsurface locations yield useful information about 3D P- and S-wave velocity model accuracy. Thus, we assert that these image volumes potentially can serve as the input into microseismic elastic velocity model building algorithms.