3D waveform inversion of microseismic data for VTI media

Abstract

3D anisotropic waveform inversion (WI) could provide high-resolution velocity models and improved event locations for microseismic surveys. Here we extend our previously developed 2D WI methodology for microseismic borehole data to 3D anisotropic models. This extension allows us to invert multicomponent data recorded in multiple boreholes and properly account for vertical and lateral heterogeneity. Synthetic examples illustrate the performance of the 3D algorithm for layer-cake and “hydraulically fractured” VTI (transversely isotropic with a vertical symmetry axis) models. In both cases, WI is able to reconstruct parts of the model which are sufficiently illuminated for the employed source-receiver geometry. We also present preliminary results for a data set from a shale play and describe a sequence of processing steps needed to make the seismograms suitable for waveform inversion. After the preprocessing, the observed and modeled direct arrivals exhibit comparable amplitude and phase characteristics and can be used for velocity analysis.