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



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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.



Geophysics, Reverse time migration (RTM), Perforation shot, Imaging, Elastic wave, Elastic, Finite difference, Staggered grid, Stress velocity, Unconventional wells, Lateral well, Bakken, Vertical seismic profile (VSP), Seismic, Seismology