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Pore Structure and Its Fractal Features of the Shale in Taiyuan Formation of Linxing Area, Ordos Basin(PDF)


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Pore Structure and Its Fractal Features of the Shale in Taiyuan Formation of Linxing Area, Ordos Basin
WU Hongchen12 HE Jinxian12 ZHANG Xiaoli1 REN Zeqiang1 ZHOU Taotao1 WANG Aikuan1
(1.School of Resources and Geoscience, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China; 2.Sichuan Province Key Laboratory of Natural Gas Geology, Southwest Petroleum University, Chengdu, Sichuan 610500, China)
Ordos basin Linxing area Taiyuan formation shale gas pore structure high-pressure mercury injection fractal dimension
The material composition of the shale of Taiyuan formation in Linxing area, Ordos basin is studied through the analysis of organic geochemistry and X-ray diffraction. The paper uses high-pressure mercury injection method to discuss pore size distribution of the shale, and analyzes mercury injection data with fractal theory to discuss the its pore heterogeneity. The results show that the TOC of the shale is 1.59%~22.58%, averaging 2.77%; the contents of brittle minerals ranges from 21.92% to 74.45%, averaging 44.55%; the contents of clay minerals ranges from 19.43% to 78.08%, averaging 52.70%. According to the result of mercury injection experiments, it is found that the pore size distribution in partial shale samples has a feature of “double peaks” , among which the larger main peak corresponds to micron-sized cracks and the smaller main peak corresponds to macropores and mesopores, while partial samples only have the main peak corresponding to cracks. Based on the matching results, fractal dimension of the pores can be divided into 2 sections, one section corresponds to micron-sized cracks with the fractal dimension ranging from 2.326 2 to 2.610 3 and the other corresponds to nano-pores such as macropores and mesopores with the fractal dimension ranging from 2.704 1 to 3.697 1. In the shale of Taiyuan formation, nanopores act as the main reservoir spaces of adsorbed gas while micro-sized cracks act as the main reservoir spaces of free gas and flowing passages. The shale samples with high content of clay minerals and low content of brittle minerals have larger fractal dimension and stronger absorption capacity to methane, which means that fracturing operation will be more difficult.




Last Update: 2018-10-09