裂缝诱导HTI双孔隙介质中的裂缝参数分析

Fracture parameters analyses in fracture-induced HTI double-porosity medium

裂缝诱导HTI双孔隙介质模型是将一组垂直排列的裂缝系统嵌入到统计各向同性的孔隙岩石基质系统中而建立的.为了研究裂缝参数对地震波在该模型中传播规律的影响,本文分别对裂缝弱度、裂缝孔隙度和裂缝渗透率这三个主要的裂缝参数进行了分析研究.数值结果表明,裂缝诱导HTI双孔隙介质中,裂缝弱度越大,介质的各向异性强度越强;与基质孔隙系统相比,裂缝系统孔隙度对介质等效孔隙度的影响很小,而裂缝系统渗透率的增大则将显著提高介质在裂缝发育方向上的等效渗透率,这符合对裂缝系统"低孔"、"高渗"特性的认识.此外,裂缝系统渗透率的增大也使慢纵波的振幅显著增强.

A fracture induced horizontal transverse isotropic （HTI） double-porosity medium has been established by embedding a set of vertical fractures into the isotropic porous background rock in previous paper. In this paper, three main parameters of the fracture system, i. e., fracture compliance, fracture porosity and fracture permeability, are studied to analyze their influence on seismic wave. The results show that the anisotropy increases with growing fracture compliance; comparing with the matrix system, the contribution of fracture porosity to equivalent porosity is small, while the influence of fracture permeability on equivalent permeability is great, which is in accord with the characteristic of low-porosity high-permeability of fracture system. Additionally, increasing fracture permeability can also enhance the amplitude of slow P-wave notably.