A matrix-fracture-fluid decoupled PP reflection coefficient approximation for seismic inversion in tilted transversely isotropic media

Fracture-induced azimuthal anisotropy of seismic waves has useful applications in the characterization of hydrocarbon reservoirs as well as the overburden. Existing theories face problems estimating the fracture-weakness parameters, identifying the saturating fluid, and constraining the depth model building. To overcome these problems, we have adopted an azimuthal amplitude variation with angle/offset inversion for the estimation of these parameters and identification of the fluid. First, we define more intuitive fracture and fluid indicators based on rock physics, identifying the fluid by decoupling the fracture weakness parameters. Then, we derive a "rock matrix-fracture-fluid" decoupled PP-wave reflection coefficient approximation of a weakly tilted transversely isotropic medium by using a perturbation matrix and scattering theory. Compared with the conventional fracture weakness-based approximation, our method incorporates the fracture density and the fluid indicator. The inversion test finds that our approximation is effective.