Abstract: The pore structure of tight sandstone formation is very complicated, which has significant effects on the percolation of oil and gas. So, elaborate characterization is needed. The fractal geometry theory has provided an effective way for the quantitative characterization of pore structure. Based on the mercury intrusion data of the tight sandstone samples collected from FY formation in Daqing oilfield company, the multiple characteristics of pore structure in tight sandstone reservoirs are quantitatively studied by the two parameters of fractal zone and fractal dimension. The results show that the microscopic pore structure of the tight sandstone samples has multiple fractal features and the numbers of fractal zones can characterize the heterogeneity of formation. The number of fractal interval is the same as the peak value of pore radius distribution curve. The more fractal interval, the stronger the heterogeneity, and the worse the porosity and permeability of reservoir. For the same sample, the larger the pore radius for fractal zones is, the stronger the heterogeneity of pore structure is. For different samples, the larger the comprehensive fractal dimension is, the more the fractal zones are and the worse the porosity and permeability of formation become.

Key words: Tight sandstone, Pore structure, Multiple fractal features, Fractal zone, Fractal dimension, Quantitative characterization

摘要： 致密砂岩储层孔隙结构复杂,对油、气渗流具有重要影响,需要精细表征,分形几何理论为孔隙结构定量表征提供了有效途径。基于大庆FY油层致密砂岩岩样压汞数据,通过分形区间和分形维数两个参数定量研究了致密砂岩储层孔隙结构的多重分形特征。结果表明,致密砂岩微观孔隙结构具有多重分形特征,其分形区间个数能够表征储层非均质性,分形区间个数与孔隙半径分布曲线峰值个数相同,分形区间个数越多,非均质性越强,储层孔、渗透条件越差。对于同一储层,孔隙半径越大的分形区间的分形维数越大,区间内孔隙结构非均质性越强。对不同储层,综合分形维数越大,分形区间越多,储层孔、渗透条件越差。

关键词: 致密砂岩, 孔隙结构, 多重分形特征, 分形区间, 分形维数, 定量表征