Feasibility of High-resolution Fracture Characterization Using Waveform Inversion

Wide-azimuth surface seismic data contain valuable information about the fracture properties, such as crack density, fluid content and fracture direction. Although this information can be obtained from standard techniques such as tomographic velocity analysis or amplitude variation with offset and azimuth, full-waveform inversion (FWI) has the potential of higher-resolution fracture characterization. Building a wavefield-based inversion framework for the fracture parameters requires identifying parameter combinations that minimize trade-offs and ensure high-resolution of the results. Using the Born approximation, which is the central ingredient of the FWI updating process, we derive the radiation patterns of different parameters of the effective orthorhombic medium formed by a vertical fracture set embedded in a VTI (transversely isotropic with a vertical symmetry axis) background. The radiation patterns describe the angular influence of each parameter, in the considered parametrization, on seismic data, and thus give insights into the resolution of the fracture properties. We show that the high-resolution recovery of crack density depends on the fracture infill, while the fracture direction might not be well-resolved because of the trade-off between different parameters.