Modeling of injection-induced seismicity in fractured rock masses with TOUGH3-seed hybrid solver

Injection of fluid in fractured reservoirs triggers seismicity that migrates away from injection point. The enlarging cloud of (micro-)seismicity can be driven by pore-fluid diffusion within fractured rock mass, thus propagating in space proportional to square root of time for an effective isotropic and homogenous medium, or by elastic-stress interactions between over-stressed pre-existing fractures.

In this contribution we adopt an hybrid approach to model seismicity evolution driven by pore-fluid propagation into a Discrete Fracture Network and apply it to a large-scale injection experiment at FORGE Test Site in Utah (USA). We couple a statistical seed model for seismicity with a physic-based solver for non-linear pore-fluid diffusion into a three-dimensional DFN (using TOUGH3). Local inelastic permeability changes mimick irreversible deformations and affect pore-fluid evolution and hence seismicity cloud.

Several synthetic catalogs are generated and compared with one generated with a pure physic-based numerical solver.