关键词: 致密砂岩, 孔隙结构, 分形特征, 表征方法, 压汞曲线

Abstract: Fractal theory provides an effective means for quantitative characterization of reservoir pore structure, while the pore structure of the tight sandstone reservoir is complicated. It needs further study that whether the conventional characterization of the fractal features of pore structure is applicable to tight sandstone reservoir or not. In this paper, present fractal characterization methods of pore structure are systematically sorted out, the applicability of each method is evaluated based on mercury injection curves of 5 tight sandstone samples, and the fractal characteristics of tight sandstone reservoir are studied. The results show that the fractal definition method can effectively characterize the fractal features of pore structure of tight sandstone, while the He Chengzu method is only applicable to tight reservoirs with permeability higher than 0.1×10-3 μm2 and the Li Kewen method is only applicable to tight reservoirs with permeability lower than 0.1×10-3 μm2, and the Brooks⁃Corey method are completely not applicable to tight sandstone reservoirs. Tight sandstone reservoir has fractal characteristics in the whole pore radius region, and no fractal features exist. Fractal dimension is an important parameter in reservoir evaluation. And the higher the fractal dimension, the worse the physical properties of reservoir, the smaller the average pore radius, the higher the displacement pressure and the higher the bound water saturation.

Key words: Tight sandstone, Pore structure, Fractal features, Characterization method, Mercury intrusion curves