煤系气储层渗透率解析模型研究进展

Research progress on analytical models of permeability for coal measure gas reservoir

渗透率是评价煤系气商业开采的重要参数之一,为了准确评价煤系气商业开采的可行性,基于天然裂缝性储层的几何模型,以及渗透率和孔隙率的立方关系、渗透率和有效应力之间的指数关系,调研分析了煤系气储层渗透率解析模型的研究现状。对影响煤系气储层渗透率的各个因素进行了分析,结果表明:气体在基质中的动力学扩散作用导致基质压力和裂隙压力不相等;面割理和端割理张开度的差异导致渗透率出现各向异性;储层为非连续介质,弹性模量随有效应力的变化而变化;有效应力系数和裂隙压缩系数对渗透率有明显的影响。基于分析结果,提出了弹性模量、有效应力系数及裂隙压缩系数的测试方法。

Permeability is one of the most important parameters for evaluating the feasibility of commercial exploitation of coal measure gas.In order to accurately evaluate the feasibility of commercial exploitation of coal measure gas,based on geometric models of naturally fractured reservoirs,the cubic law of permeability and porosity and the exponential relationship between permeability and effective stress,the research status of analytical models of permeability for coal measure gas reservoirs is investigated and analyzed.The factors affecting permeability are analyzed and the results show that,the dynamic diffusion of gas in the matrix results in unequal matrix pressure and fracture pressure;the anisotropy of permeability is caused by the difference in the opening of surface and end cleats;coal measure gas reservoir is a discontinuous medium and the elastic modulus varies with the change of effective stresses;the effective stress coefficient and fracture compressibility have a significant effect on permeability.According to the analysis,the test method of the elastic modulus,the effective stress coefficient and fracture compressibility is proposed.