High precision inversion method for two-phase complex fracture media based on linear slip theory

Fractures are the channel of oil and gas storage and migration, and also the inducing factor of mine disaster. Therefore, a detailed characterization of fractures contributes to safe and effective development of resources. Traditional fracture prediction based on linear slip theory usually assumes that the fracture is horizontal or vertical, which is not consistent with the natural morphology of the fracture. Moreover, using approximate solutions to solve the weak seismic response of fractures is easy to cause errors, and the assumption of single-phase media is not consistent with the geological conditions of oil and gas reservoirs. To address these issues, an exact Zoeppritz equation is proposed for two-phase complex fracture media inversion. The compliance parameter, which can describe the fracture characteristics, are introduced into the Zoeppritz equation, and the reflection and transmission coefficients of the two-phase complex fracture media are derived. Multiscale inversion is an effective means to balance the energy difference between fractures and impedance interfaces. Therefore, a comprehensive multiscale inversion process combining exact and approximate solutions is proposed. The edge preserving smoothing (EPS) has a good boundary protection effect. Introducing EPS into the inversion objective function can highlight the boundaries of small-scale geological structures, which is conducive to the fine characterization of fractures. Test results of synthetic and field data show that the proposed inversion method can obtain high-precision elastic and compliance parameters, and is an effective tool for fine characterization of fracture media in oil and gas development and carbon geological storage projects.