储层岩石孔隙的分形结构研究和应用

FRACTAL TEXTURE RESEARCH ON THE PORES IN RESERVOIR ROCKS AND ITS APPLICATION

文章根据分形理论推导出了多孔介质中孔隙分布的两参数分形几何公式 ,建立了利用压汞资料计算孔隙分形维数来分析孔壁的粗糙度和孔径分布的不均匀程度的研究方法。将该方法应用于四川砂岩和碳酸盐岩气藏低渗透储层改造措施研究 ,结果发现 ,无论是盐酸酸化碳酸盐岩还是土酸酸化砂岩 ,入口处的毛管半径均明显增加 ,但分形维数的变化不同 ,碳酸盐岩酸化后分形维数均有不同程度的增加 ,砂岩酸化后无明显变化或有所减小。因此 ,碳酸盐岩酸化易于形成不均匀的酸蚀孔道 ,而砂岩酸化更倾向于均质溶蚀。储层岩石的分形几何研究有可能成为研究储层特征、成岩作用和储层分类的重要依据和新手段。

In the paper,a two parameter fractal geometric formula expressing pore distribution in porous media is derived according to fractal theory and a research method of analyzing pore wall roughness and the heterogeneity of pore diameter distribution is proposed through calculating pore fractal dimension by use of mercury injection data.In light of the research on low permeability reservoir deformation of the sandstone and carbonate gas reservoirs in Sichuan Basin by this method,it was found that no matter whether the carbonate rock was acidized by hydrochloric acid or the sandstone by mud acid,the capillary radii at entrance holes were obviously enlarged;however,the change in fractal dimension was different,i.e.the fractal dimension of the carbonate rock after having been acidized increased to various degrees and that of the sandstone after having been acidized had a little change or decreased to a certain degree.Therefore,the carbonate rock acidized is easy to form heterogeneous erosion channels and the sandstone acidized is more inclined to forming a homogeneous erosion.The fractal geometric research on reservoir rocks is able to become an important basis and new means of studying reservoir properties,diageneses and reservoir classification.