裂缝-孔隙介质储层渗透率表征及其影响因素分析

含裂缝多孔介质渗透率预测是非常规油气资源勘探开发的一个紧迫问题.现有多孔介质岩石物理模型通常利用圆形孔管模拟宏观岩石孔隙空间，难以定量描述软孔隙/裂缝在压力作用下的闭合情况，缺乏裂缝/孔隙间流量交换的连通机制.本文提出含三维裂缝/软孔隙网络多孔介质模型，将储层岩石裂缝/软孔隙表示为椭圆截面微管，建立了周期性压力作用下微观裂缝流量表达式，通过网络模型和流量守恒条件，得到含有三维裂缝/软孔隙网络的多孔介质渗透率计算方法.数值算例表明，预测结果与实验数据分布范围吻合很好，能够给出不同类型岩心对应孔隙纵横比的分布图.三维裂缝/软孔隙网络模型建立了宏观可观测量与裂缝参数之间关系，能够定量分析岩石渗透率随裂缝体密度、纵横比、孔隙流体类型和围压等因素的变化规律，为复杂条件下储层渗透率预测提供了一种有效方法.

Characterization of reservoir permeability and analysis of influencing factors in fracture-pore media

Permeability prediction of porous media with fractures is an urgent problem in unconventional oil and gas exploration and development. Conventional rock-physics models of porous media usually use circular pore/tubes to simulate macroscopic rock pore space, which is difficult to quantitatively describe the closure of soft pores/fractures under pressure and lacks the connectivity mechanism of flow exchange between fractures/pores. In this paper, a three-dimensional fracture/soft pore network model is proposed. Fractures and soft pores in reservoir rocks are expressed as elliptical cross-section microtubules. The fluid flow velocity field in fracture/pore space is established under the action of periodic pressure. In terms of the network model and the conditions of flow conservation, we establish the permeability calculation method for three-dimensional fracture/soft porous media. Numerical examples show that the predicted results are in good agreement with the distribution range of experimental data. And the distribution of pore aspect ratio corresponding to different types of cores can be predicted. The three-dimensional fracture/soft pore network model establishes the relationship between macroscopic observable measurement and fracture parameters. It is possible now to quantitatively analyze the variation of rock permeability with the racture density, aspect ratio, pore fluid type, confining pressure and other factors, which provides an effective approach to reservoir permeability prediction under complex conditions.