Linear-slip discrete fracture network model and multiscale seismic wave simulation

Abstract

We propose a method to design a discrete fracture network (DFN) model for seismic wave simulations that eliminates complex meshing requirements and poor mesh design. An ant-tracking volume is generated from the original seismic to capture the global fracture geometry. A mesh structure is specified prior to adding fractures. Fractures are then specified on the mesh in the form of small fracture patches following the trend of ant-tracking signals in the previously defined mesh. In the proposed method, the implementation of the DFN model is thus independent of the mesh structure. Also, fracture clusters in the final DFN model are composed of multiple small patches, and each small patch is represented by the linear slip model in the form of a discontinuity of the displacement field. We also performed wave simulations to validate the proposed method of DFN model building, and investigated the wave behavior in the given fracture structure. For efficient implementation of wave modeling, we employed the generalized multiscale finite element method to discretize the elastic wave equation with explicit fractures. The wave simulation results show that a small fracture segment could be ignored when the wavelength is long enough; however, fracture clusters can induce large displacement discontinuities and wave scattering, and these effects become obvious as we apply high source frequency.