新疆石油地质

›› 2018, Vol. 39 ›› Issue (5): 1-1.doi: 10.7657/XJPG20180508

• 论文 •    

鄂尔多斯盆地临兴地区太原组页岩孔隙结构及分形特征

吴泓辰1，2，何金先1，2，张晓丽1，任泽强1，周逃涛1，王爱宽1   

  1. (1.中国矿业大学 资源与地球科学学院,江苏 徐州 221116;2.西南石油大学 天然气地质四川省重点实验室,成都 610500)
  • 出版日期:2019-01-01 发布日期:1905-07-18

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

WU Hongchen1,2, HE Jinxian1,2, ZHANG Xiaoli1, REN Zeqiang1, ZHOU Taotao1, WANG Aikuan1   

  1. (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)
  • Online:2019-01-01 Published:1905-07-18

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摘要： 通过有机地球化学、X射线衍射等分析，对鄂尔多斯盆地临兴地区太原组页岩的物质组成特征进行了研究，利用高压压汞法探讨了页岩孔径分布特征，并利用分形理论对压汞数据进行了分析，以探讨页岩孔隙非均质性。结果表明，研究区页岩有机碳含量为1.59%~22.58%，平均为2.77%；脆性矿物含量为21.92%~74.45%，平均为44.55%；黏土矿物含量为19.43%~78.08%，平均为52.70%.根据压汞测试结果，部分页岩样品孔径具有“双峰式”的分布特点，较大的主峰对应微米级裂隙，较小的主峰对应大孔与介孔，而部分页岩样品孔径仅有裂隙对应的主峰。根据拟合结果，孔隙的分形维数可分为两段，第一段对应微米级裂隙，其分形维数为2.326 2~2.610 3；第二段对应大孔和介孔等纳米级孔隙，其分形维数为2.704 1~3.697 1.太原组页岩中，较小的纳米级孔隙是吸附态气体的主要储集空间，而较大的微米级裂隙主要作为游离态气体的储集空间及渗流通道。黏土矿物含量高而脆性矿物含量较低的页岩样品分形维数更大，对甲烷有着更强的吸附能力，但同时对压裂改造有着更高的要求。

Abstract: 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.

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