Abstract
Recently, the petroleum industry has shown an increasing interest in fractured reservoirs. Aligned fractures in the form of fracture swarms or fracture corridors can induce azimuthal anisotropy in rocks. The aim of this paper is to investigate the seismic wavefield in the vicinity of fracture corridors. We study two mainstream equivalent medium theories: Hudson's model and Schoenberg's linear slip model, and discuss their application conditions and limitations. We choose Schoenberg's theory to calculate the effective stiffness matrix of discrete fractures and use a finite difference method to stimulate the 3D elastic wavefields of fractured media. Fracture-induced anisotropy is also included in this paper. Then, we investigate the indicator of fluid inclusions in fractures: the normal to tangential compliance ratio ZN /ZT and conclude that dry fractures produce typical elliptical anisotropy which is much easier to identify. Finally, we analyze characteristics of the seismic response of fracture corridors based on the synthetic shot gathers and azimuth gathers in terms of elliptical anisotropy and shear wave splitting.
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