页岩气储层孔隙特征差异及其对含气量影响

Pore characteristics of a shale gas reservoir and its effect on gas content

吴艳艳 曹海虹 丁安徐 王亮 陈云燕

Wu Yanyan Cao Haihong Ding Anxu Wang Liang Cheng Yunyan

中国石化 华东分公司 石油勘探开发研究院实验中心, 江苏 扬州 225000

Experiment Center, Petroleum Exploration and Development Institute, SINOPEC East China Company, Yangzhou, Jiangsu 225000, China

运用氩离子抛光+扫描电镜和氮气吸附法对渝东南地区龙马溪组的24个页岩样品和川东南地区须家河组10个页岩样品孔隙进行测试,探讨页岩的孔隙特征差异及其对含气量的影响。研究发现,其孔隙类型主要包括有机质孔、矿物粒间孔、溶蚀孔、晶间孔、矿物层间解理缝和微裂缝等;孔隙形态多为不规则,多呈开放状态;孔隙结构较复杂,纳米级有机质孔丰富,主孔位于2~10 nm。须家河组页岩样品以无机中大孔和微裂隙为主。有机质孔发育差异原因可能是由页岩的有机质类型本身化学分子性质差异造成,也可能是具有催化生气作用的无机矿物或元素与有机质赋存关系差异造成。数理统计结果显示,孔隙类型并不是含气量大小的主控因素,TOC是页岩气藏最本质因素。须家河组页岩中孔隙结构主要受无机矿物影响;龙马溪组页岩样品的TOC是比表面积和孔径为2~10 nm孔发育的本质因素,提供页岩气主要的储存空间。伊利石是孔径为2~10 nm孔发育的重要影响因素,也是提供页岩气存储空间的重要物质。

The porosity tests of 24 Longmaxi Formation shale samples fromthe southeastern Chongqing area and 10 Xujiahe Formation shale samples fromthe southeastern Sichuan area were carried out with argon ion milling+ scanning electron microscopy (SEM) and nitrogen adsorption methods. The effect of porosity difference on gas content was discussed. Shale pores are usually organic pores, mineral inter-particle pores,dissolution pores, inter-granular pores and inter-laminar cleavage cracks, and most of the pore shape was irregular and open.The pore structure of the samples was complex. Nano-scale organic pores were common in the Longmaxi Formation shale samples, and the pore diameter was 2-10 nm. Inorganic middle-large pores and micro-cracks were dominant in the Xujiahe Formation shale samples. The pore characteristics might result from different chemical mole-cular properties of organic matter in the shale, or a catalytic relationship between inorganic mineral or element and organic matter. Statistical results showed that the pore types were not the main controlling factors of gas content: TOC was the most essential factor for shale gas reservoir.The pore structure of the Xujiahe Formation shale samples was mainly affected by inorganic minerals.TOC was the dominant factor of specific surface area and 2-10 nm pores in the Longmaxi Formation shale samples, and provided the main storage space for shale gas.Illite was an important factor for 2-10 nm pores, which provided the main storage space for the Xujiahe shale gas.

中国石化科技项目(P12014)资助。

https://doi.org/10.11781/sysydz201502231