Fluid Pressure Diffusion in Fractured Media: The Role Played by the Geometry of Real Fractures

Abstract

AbstractWave‐induced fluid pressure diffusion (FPD) represents an important mechanism of seismic energy dissipation in fractured media. The associated effects on wave propagation are typically studied considering idealized fracture geometries. Here, we study fracture‐geometry‐related effects on FPD by numerically computing the frequency‐dependent and angle‐dependent seismic velocity and attenuation on models having fractures of realistic geometries. The geometry of the models is derived from microcomputed tomography images of a fractured Berea sandstone. By comparing the numerical results with those for an equivalent thin‐planar‐layer analytical model, we isolate fracture‐geometry effects. We found that discrepancies on the anisotropic behavior of P and S waves with respect to the simple analytical model are small except for the S wave attenuation. This is associated with the pressure gradients induced by S waves in fractures exhibiting a mild curvature. Part of this dissipation occurs inside the fracture, parallel to its walls, and is thus controlled by its permeability, which points to a possible perspective of inferring fracture hydraulic properties from S waves attenuation.