盐岩分形迂曲度模型与渗透率表征研究

Study on the salt-rock fractal tortuosity model and characterization relationship of permeability

孔道迂曲度是描述岩石渗流通道、解决渗透率几何表征及理论表达的关键参量.盐岩作为微纳米尺度裂隙网络介质,复杂的流通网络形成的高迂曲度导致了超低渗透率.为进行微纳米尺度裂隙网络介质渗透率研究,基于Poiseuille公式获得了毛细管压力、饱和度与迂曲度的半理论半经验关系式.进而开展低速与高压压汞实验,获得低渗盐岩迂曲度数据,建立了迂曲度与渗透率、孔隙度的关系模型,并揭示了其为非线性关系.引入迂曲系数,定义其为迂曲度与迂曲度分形维数的乘积,发现渗透率与迂曲系数呈线性对数关系.研究结果可以为微微纳米尺度裂隙网络介质渗透率研究提供一个参考依据。

The tortuosity is a key parameter to describe the percolation channel and solve the geometrical representation and theoretical expression of permeability. In micro-nano fracture network media such as salt rocks,the study of permeability of low-permeability salt rock is more complicated. In order to study the permeability of micro-nano fracture network media, this paper derives the relationship between capillary pressure, mercury saturation, and tortuosity with the Hagen-Poiseuille equation and uses the mercury injection data to calculate the tortuosity of salt rock. The results which established the relationship between tortuosity, permeability, and porosity are compared with those of previous researchers. Introducing the fractal dimension and defined fractal tortuosity coefficient as the product of tortuosity and fractal tortuosity dimension. The relationship between the fractal tortuosity coefficient and the permeability is summarized in this paper, and there is a linear relationship between the two. The results can provide a reference for the study of the permeability of micro-nano fracture network media.