3D Numerical Simulation of Elastic Wave Propagation in Discrete Fracture Network Rocks

Fractures play an important role in controlling rock block stability and the hydraulic properties of fractured rock formations. Understanding elastic wave propagation in fractured media can result in significant advances for the geophysical prediction of fracture parameters from seismic data. However, most natural fracture characteristics, such as fracture length, aperture, angle and location are random; therefore, fracture models must be built discretely and follow some stochastic principles. We construct stochastic models of fractured rock samples using a random fracture network rather than a single fracture. Three-dimensional (3D) wave field computation is a computationally complex problem. Here, the 3D fourth-order in space, second-order in time, displacement-stress staggered-grid finite-difference scheme is used for accurate simulations. Our numerical examples demonstrate the effects of varying fracture number, aperture, and length distribution of the fracture network on the seismic response. The wave field scattering caused by the contrast between fractures and background media is one of the key features, and the resulting scattering is more obvious for S-waves than for P-waves. Such an approach can be applied to any fracture network model that provides a link between fracture parameters and seismic attributes.