川南地区五峰组—龙马溪组页岩微观孔隙结构特征及主控因素

为研究川南地区五峰组-龙马溪组页岩储层的孔隙结构特征及主控因素，对9口取心井的页岩样品开展了有机地球化学、X射线衍射全岩矿物含量及黏土矿物相对含量分析、氩离子抛光扫描电镜观察、高压压汞测试和气体（CO₂和N₂）等温吸附实验等研究。结果表明：①页岩总有机碳（TOC）质量分数平均为2.42%，等效镜质体反射率（R_o）平均为2.83%，有机质处于过成熟阶段；黏土矿物以伊/蒙混层-伊利石-绿泥石组合为主，处于晚成岩阶段。②页岩的平均孔隙度为2.49%，孔径主要为2.6~39.8 nm，以细颈墨水瓶状和狭缝孔为主；饱和吸附气质量体积为0.014 7~0.032 2 cm³/g，总孔隙比表面积为19.49~40.68 m²/g，介孔和宏孔为页岩气的储集提供了主要储集空间，微孔对孔隙的比表面积贡献较大。③TOC，R_o和黏土矿物相对含量等均对微孔和介孔的比表面积具有一定的控制作用，黏土矿物层间孔的发育程度对介孔和宏孔的孔隙体积具有一定的影响，脆性矿物含量与微孔、介孔、宏孔的孔隙体积均呈负相关关系。该研究成果对川南地区寻找优质储层和页岩气富集区均具有指导作用。

Characteristics of microscopic pore structures and main controlling factors of Wufeng-Longmaxi Formation shale in southern Sichuan Basin

To study the pore structure characteristics and main controlling factors of Wufeng-Longmaxi Formation shale in southern Sichuan Basin, the organic geochemistry, X-ray diffraction analysis of whole rock mineral content and clay mineral content, scanning electron microscopy of argon ion polishing, high pressure mercury injection test and gas (CO₂ and N₂) isothermal adsorption experiments were carried out on shale samples from nine coring wells. The results show that:(1) The average TOC mass fraction of shale is 2.42%, the average vitrinite reflectance (R_o) is 2.83%, and the organic matter is in over-mature stage. The clay minerals of shale are mainly composed of mixed-layer minerals of illite and montmorillonite, illite and chlorite, so it is in the late diagenetic stage. (2) The average porosity of shale is 2.49%, and pore size is mainly 2.6-39.8 nm, with bottle-shaped and slit holes of fine-necked ink. The mass volume of saturated absorbed gas is 0.0147-0.0322 cm³/g, and the specific surface area of total pores is 19.49-40.68 m²/g. Mesopores and macropores provide the main reservoir space for shale gas reservoir, while micropores contribute greatly to the pore surface area. (3) TOC content, degree of thermal evolution and clay mineral content all have a certain controlling effect on specific surface area of micropores and mesopores, the development degree of interlayer pore has an effect on the mesopore and macropore volume, and the content of brittle minerals is negatively correlated with the volume of micropore, mesopore and macropore. The study results have a guiding role in searching for high-quality reservoirs and shale gas enrichment areas in the southern Sichuan Basin.