Amplitude variation with angle and azimuth inversion to estimate fracture properties in shale-gas reservoirs

Abstract

Seismic amplitude variation with angle and azimuth inversion is an effective tool for estimating subsurface anisotropic properties from seismic data. Generally, existing methods are oriented toward obtaining elasticity constants, anisotropic coefficients or fracture weaknesses, which are not direct indicators for the exploration and development of hydrocarbons, unlike fracture parameters. Moreover, the conversion from elastic to fracture parameters is based on models subject to error propagation. To overcome these problems, the fracture weaknesses are formulated as a weighted representation of fracture density and aspect ratio and fluid properties. Then, an inversion method is proposed that incorporates the fracture aspect ratio as a spatial variable, which can be applied to estimate water saturation and permeability. Compared with the conventional methods, our approach yields more geological information, as shown by an application to real data.