页岩中单体有机质孔隙演化的原位热模拟实验

In-situ thermal simulation experiment of single organic matter pore evolution in shale

席斌斌 潘安阳 鲍芳 卢龙飞 曹涛涛 王晔 马中良 刘显

XI Binbin PAN Anyang BAO Fang LU Longfei CAO Taotao WANG Ye MA Zhongliang LIU Xian

中国石化 油气成藏重点实验室, 江苏 无锡 214126 页岩油气富集机理与高效开发全国重点实验室, 江苏 无锡 214126 中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214126 湖南科技大学 页岩气资源利用与开发湖南省重点实验室, 湖南 湘潭 411201 长安大学 西部矿产资源与地质工程教育部重点实验室, 西安 710054

SINOPEC Key Laboratory of Petroleum Accumulation Mechanisms, Wuxi, Jiangsu 214126, China State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Efficient Development, Wuxi, Jiangsu 214126, China Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China Hunan Provincial Key Laboratory of Shale Gas Resource Exploitation, Hunan Universityof Science and Technology, Xiangtan, Hunan 411201, China Key Laboratory of Western Mineral Resources and Geological Engineering of Ministryof Education, Chang'an University, Xi'an, Shaanxi 710054, China

有机质孔隙是我国南方页岩气重要的储集空间，而有机质类型与有机质孔隙发育息息相关。为实现单体有机质孔隙演化过程的原位观测，揭示下古生界页岩显微组分热解过程中的孔隙演化过程，以低成熟度的美国俄亥俄上奥陶统页岩以及欧洲波罗的海东部下志留统页岩为研究对象，联合运用飞秒激光、冷热台、显微镜以及扫描电镜等技术，实现页岩中单体有机质孔隙演化过程的原位观测，进而辨别不同类型有机质的孔隙发育过程和演化规律。对低成熟度的“倾气”型笔石以及“倾油”型层状藻类体孔隙热演化过程的原位观测分析结果表明：(1)笔石的体积开始发生明显变化的起始温度要高于层状藻类体，生烃演化要晚于层状藻类体；(2)笔石和层状藻类体在热演化过程中均形成了明显的收缩缝，但就形成收缩缝的规模而言，笔石明显较小，生烃转化率要低于层状藻类体；(3)笔石与层状藻类体内部孔隙的演化存在明显的差异，笔石原有的生物组织孔在高温阶段发生了明显的扩容并且有新的内部孔隙生成，而层状藻类体在整个热演化过程中并未形成内部孔隙，证实了“生气窗”是有机质孔隙大量发育的主要阶段。有机质组成以及结构的不同可能是造成上述两种有机质孔隙演化过程存在差异的主要原因。

Organic matter pores is the most important shale reservoir space in South China, and the types of organic matter influence the formation and evolution process of organic matter pores. In order to achieve in-situ observation of the pore evolution process of single organic matter and reveal the pore evolution process during the pyrolysis of the macerals of the Lower Paleozoic shale, this paper focuses on the low-maturity Upper Ordovician shale from Ohio, USA and the Lower Silurian shale in the eastern Baltic Sea, Europe. By using femtosecond laser, cooling-heating stage, microscope and SEM techniques, the in-situ observation of pore evolution of the single organic matters in shale can be realized, and the pore development process and evolution law of different types of organic matters can be distinguished. The in-situ observation results of pore thermal evolution process of low-maturity "gas-prone" graptolite and "oil-prone" lamalginite show that: (1) The initial temperature of obvious volume change of graptolite is higher than that of lamalginite, which infers that the hydrocarbon generation of graptolite is later than that of lamalginite. (2) Both graptolite and lamalginite generated obvious shrinkage cracks during thermal evolution process, but the scale of shrinkage cracks of graptolite is smaller than that of lamalginite, indicating that the hydrocarbon-generating transformation ratio of graptolite is lower than that of lamalginite. (3) There is an obvious difference between graptolite and lamalginite in the evolution of internal pores: the intrinsical biopores of graptolite were enlarged and some new internal pores were formed during the high temperature stage, but no new internal pores of lamalginite were observed during the whole process of thermal evolution, which infers that "gas-generating window" is the main stage of organic matter pore development. Moreover, the difference in the composition and structure of organic matters may be the main reason for the difference in pore evolution of graptolite and lamalginite.

国家自然科学基金青年基金 42002136;国家自然科学基金 42072156;企业创新发展联合项目 U19B6003-03

https://doi.org/10.11781/sysydz2023051016