关键词: 砂砾岩, 孔隙结构, 孔隙类型, 高压压汞, 分形维数

Abstract:

Based on data from cast thin section, microscope, mercury-injection and conventional physical property analyses, we investigated the fractal characteristics of pore structure of glutenite reservoir developed in the Eocene Liushagang Formation of the Wushi Sag. The study includes the characteristics of fractal curves, fractal dimension and its relationship with reservoir physical properties and pore structure parameters, the effectiveness of fractal dimension in characterizing the storage and the permeability of different types of sandstones. The results show that compared with conventional sandstone, the high-pressure mercury fractal curve of glutenite presents has segmented features, indicating the development of three sets of pore-throat systems of different scales (macropores, small pores, and micropores). Segmented fractal characterization indicates that the fractal dimensions of large and small pores are greater than those of conventional sandstone. All the above analysis shows that the glutenite pore structure is the most complex. The fractal dimension of conventional sandstone has a good relationship with porosity and permeability, while the fractal dimension of glutenite samples has only a minor correlation with the storage capacity parameters. Hence, the glutenite has complex porosity-permeability relations, diverse types of pores and pore connectivity. The fractal dimension can characterize the reservoir capacity, but has certain limitation on seepage capacity characterization.

Key words: glutenite, pore structure, pore type, mercury-injection, fractal dimension