川南下寒武统筇竹寺组页岩孔隙结构特征及其主控因素

Pore Structure Characteristics and Main Controlling Factors of Qiongzhusi Formation Shales of Lower Cambrian, Southern Sichuan Basin

罗思聪 张南希 王保保 周桦 王同

LUO Sicong ZHANG Nanxi WANG Baobao ZHOU Hua WANG Tong

中国石化西南油气分公司勘探开发研究院, 四川 成都 610041

Exploration & Production Research Institute of Southwest Petroleum Branch, SINOPEC, Chengdu, Sichuan 610041, China

为评价川南筇竹寺组两类页岩储层特征及差异，基于钻井系统取芯资料，综合运用X衍射、氩离子抛光扫描电镜、高压压汞、低温N$_2$和CO$_2$吸附等实验方法，对两类页岩储层TOC含量、矿物组成、微观孔隙类型、孔隙结构特征及其影响因素开展了研究。研究表明，两类页岩储层均发育多种类型微观孔隙，整体以无机孔为主，富有机质页岩有机孔占比高于含有机质页岩；含有机质页岩(TOC含量 < 1%)孔隙度为4.78%$\sim$6.02%(平均5.22%)，储层孔径以20$\sim$100 nm为主，宏孔为主要储集空间(平均70.10%)；富有机质页岩(TOC含量$\geqslant$1%)孔隙度为3.88%$\sim$7.06%(平均5.53%)，储层孔径分布以1$\sim$50 nm为主，介孔为主要储集空间(平均81.81%)。含有机质页岩微孔比表面积和体积与TOC含量成正相关关系，而富有机质页岩微孔、介孔比表面积和体积均与TOC含量成正相关关系；两类页岩储层与矿物组成关系复杂，石英和长石构建的支撑结构奠定了原始无机孔基础，TOC、黏土矿物及后期成岩矿物等充填于粒间孔改变了孔隙结构，TOC含量的增多在一定程度上提高了有机孔占比。

To assess the characteristics and differences of the two types of shale reservoirs within the Qiongzhusi Formation of southern Sichuan Basin, based on the systematic coring data from drilling, a comprehensive application of experimental methods such as X-ray diffraction, argon ion polishing scanning electron microscopy, high-pressure mercury intrusion, low-temperature N$_2$ and CO$_2$ adsorption was employed to conduct research on the TOC content, mineral composition, microscopic pore types, pore structure characteristics, and their influencing factors of the two types of shale reservoirs. The research results indicate that both types of shale reservoirs develop multiple types of microscopic pores, and the overall pore type is mainly inorganic pores. The proportion of organic pores in the organic-rich shale is higher than that in the shale with organic matter. The porosity of the organic-bearing shale (TOC < 1%) ranges from 4.78% to 6.02% (average 5.22%), and the pore size distribution of the reservoir is mainly 20$\sim$100 nm, with macropores being the main reservoir space (average 70.10%). The porosity of the organic-rich shale (TOC $\geqslant$ 1%) ranges from 3.88% to 7.06% (average 5.53%), and the pore size distribution of the reservoir is mainly 1$\sim$50 nm, with mesopores being the main reservoir space (average 81.81%). The specific surface area and volume of micropores in the organic-bearing shale have a positive correlation with the TOC content, while the specific surface area and volume of micropores and mesopores in the organic-rich shale have a positive correlation with the TOC content. The relationship between the two types of shale reservoirs and the mineral composition is complex. The supporting structure constructed by quartz and feldspar lays the foundation of the original inorganic pores, and TOC, clay minerals, and post-diagenetic minerals filling the intergranular pores change the pore structure, and the increasing content of TOC can improve percentage of organic pores.

10.11885/j.issn.1674 5086.2024.12.05.04