Elastic Reverse-Time Migration Imaging Using Perforation Shots and Vertical Receiver Arrays

Recent innovations in hydraulic-fracture stimulation have increased the prevalence of borehole seismic monitoring of microseisms. This research investigates elastic-wave propagation as it pertains to seismic sources within the local borehole vicinity and the utility of elastic-wave finite-difference solutions as a means to model elastic-wave propagation and as a kernel component in a reverse-time migration imaging condition. A 2-D fourth order spatially accurate finite-difference solution to the elastic-wave equation is implemented to model wave propagation in elastic media resulting from a variety of focal-mechanism types and orientations. This algorithm’s simulated wavefield is compared to that of a preexisting finite-difference solution implementation in seismic Unix’s suea2df and an approximate analytic solution to the elastic-wave equation. A modified elastic reverse-time migration imaging condition is presented and tested on synthetic data propagated through a single-diffractor, two horizontal interfaces, and a subset of the Marmousi 2 model. Each test case simulates common acquisition geometries encountered in a perforation shot monitoring in an unconventional well and is demonstrated to be a potentially feasible imaging technique for near borehole subsurface structure. Imaging quality is then demonstrated to be dependent on acquisition geometry as described by the Nyquist sampling theorem. The reverse-time migration algorithm is then invoked on a dataset acquired from a vertically oriented receiver array by Hess Oil Co. from perforation shots in the En-Person 3H well.