Time-lapse Changes of Anisotropic Rock Properties Caused by Hydraulic Fracture Stimulations at the First EGS Collab Testbed

A continuous active source seismic monitoring (CASSM) system is deployed at the first EGS Collab testbed for monitoring hydraulic fracture stimulations. Four fracture-parallel and two orthogonal wells with 24 hydrophones, 18 accelerometers, and 17 dipole sources are used to acquire CASSM data during hydraulic fracture stimulations. Previous 3D anisotropic traveltime tomography and anisotropic elastic-waveform inversion results of the campaign cross-borehole seismic data reveal that the rock within the stimulation region is anisotropic and heterogeneous. We use these results as the initial models and apply 3D anisotropic first-arrival traveltime tomography and 3D anisotropic elastic-waveform inversion to the CASSM data acquired before and after stimulations in May, 2019 and December, 2019. We observe some regions with time-lapse changes in seismic velocities and anisotropy parameters caused by hydraulic fracture stimulations.