页岩中有机质孔隙非均质性的微观结构及电镜—拉曼联用研究

Microstructure and SEM-Raman study of organic matter pore heterogeneity in shale

鲍芳 俞凌杰 芮晓庆 张庆珍 范明 马中良

BAO Fang YU Lingjie RUI Xiaoqing ZHANG Qingzhen FAN Ming MA Zhongliang

中国石化 油气成藏重点实验室, 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

SINOPEC Key Laboratory of Petroleum Accumulation Mechanisms, Wuxi, Jiangsu 214126, China Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China

页岩中有机质孔隙的发育特征及其影响因素对我国页岩气勘探开发具有重要意义。扫描电镜下观察发现页岩中有机质的孔隙发育常见非均质性，但现阶段由于缺乏有效的微区研究方法，有机质孔隙发育的影响因素仍存在较大的争议。选取四川盆地平桥地区下志留统龙马溪组黑色页岩，利用氩离子抛光-扫描电镜、FIB-SEM三维分析技术，从二维和三维层面对页岩中有机质孔隙的非均质性特征进行了分析。不依赖于有机质显微组分类型，只考虑有机质的孔隙发育程度，将不同孔隙发育程度的有机质分为3个级别，并利用大面积背散射成像（MAPS）分析方法对这三种有机质的面积占有率和对孔隙的贡献度分别进行了定量分析；采用扫描电镜-激光拉曼联用技术分析其拉曼光谱，利用拉曼参数的差别探讨了影响有机质孔隙发育非均质性的主要因素。不同孔隙发育程度有机质的D峰与G峰强度比不同，说明不同有机质的芳香结构有序度有较明显的区别，表明影响有机质孔隙发育的主要因素为原始有机质的组成。该方法能够在微区观察有机质孔隙的同时，原位分析有机质显微组分的分子结构特征，明确有机质孔隙发育的主要影响因素。

The characteristics and influencing factors of pore development in organic matters of shale are of great significance for shale gas exploration and production in China. The pore development in organic matters of shale has been found to be heterogeneous with SEM observation. However, due to the lack of effective approach for micro-scale research, the influencing factors of pore development of organic matter are still controversial. Black shale samples of the Longmaxi Formation of Pingqiao area of the Sichuan Basin were selected by this study and the heterogeneity of development and distribution of pores in organic matters were analyzed in detail from two-dimensional and three-dimensional levels by the means of Ar ion polishing SEM and FIB-SEM observation. The organic matters with different pore development degrees were divided into three levels, and the area occupancy and contribution to the pores of these three levels of organic matter were studied by MAPS. In this paper, the Raman spectrum of three levels of organic matter with different pore development were obtained by SEM-Raman. The main factors affecting the heterogeneity of pore development of organic matter were discussed in view of the differences of Raman parameters. The results showed that the intensity ratio of D peak to G peak of organic matter was different, which indicated that the order degree of aromatic structure of different organic matter was significantly different, proving that the main factor affecting the pore development in organic matter could be the composition of original organic matter. This method can be used to observe the pores of organic matter in micro area and analyze the molecular structure characteristics of organic matter macerals in-situ, and further clarifies the main influencing factors of pore development of organic matter.

国家自然科学基金 42072156

https://doi.org/10.11781/sysydz202105871