Seismic Signatures of Fractured Reservoirs: Theory Versus Numerical Simulations

Abstract

Seismic attenuation and dispersion usually occur in the fractured reservoirs. The wave-induced fluid flow (WIFF) is recognized as an important mechanism for these phenomena. In this work, we study the seismic attenuation and dispersion due to WIFF in saturated rocks containing two orthogonal sets of intersecting fractures. Based on the existing unified model for the WIFF, we proposed the theoretical model for three types of fractures: periodic planar fractures, randomly-spaced planar fractures, and penny-shaped cracks. The 2D synthetic rock sample with intersecting fractures is then studied by both numerical simulations and the proposed theoretical model. The numerical simulations are carried out using an upscaling method based on Biot’s quasi-static equations of poroelasticity. We find a good agreement between the theoretical predictions and the numerical simulations. For the WIFF between fractures and the background, the seismic dispersion and attenuation predicted by the theoretical model for penny-shaped cracks are in best agreement with the numerical simulation results. On the other hand, for the WIFF between connected fractures, it turns out that the theoretical model for periodic planar fractures is best. The proposed theoretical approach can be applied to both 2D and 3D fracture systems, which can thus constitute a useful tool for the characterization of reservoirs with intersecting fractures.