渝东南地区海相页岩有机质孔隙发育特征及演化

页岩气在储层内的有效赋存及渗流由有机质孔隙决定。由此，以渝东南地区下志留统龙马溪组和下寒武统牛蹄塘组高—过成熟度典型富有机质黑色海相页岩为研究对象，使用电子显微镜观察2套页岩层位的有机质孔隙结构。结果表明：龙马溪组页岩有机质孔隙主要发育在焦沥青内部，而固体干酪根内仅发育少量直径较小的有机质孔隙；牛蹄塘组页岩的焦沥青和固体干酪根均不发育有机质孔隙；2套页岩的总有机碳含量、全岩矿物组成及干酪根类型均具有相似特征，但牛蹄塘组页岩的热成熟度要远高于龙马溪组页岩，且已达到变质期，其固体干酪根和焦沥青的物理化学性质均趋近于石墨，导致其有机质内部不发育孔隙。过高的热成熟度不利于页岩中有机质孔隙的保存，所以渝东南地区下寒武统牛蹄塘组高—过成熟度海相页岩气的勘探开发应重点寻找热成熟度低于3.5%的地区。

Development characteristics and evolution of organic matter pores of marine shale in southeastern Chongqing

Organic matter pores determine the occurrence and effective flow of hydrocarbon gas in shale reservoir. The organic matter pore structures of typical organic-rich black marine shale with high-over maturity of Lower Silurian Longmaxi Formation and Lower Cambrian Niutitang Formation in southeastern Chongqing were observed by electron microscope. The results show that there were a large number of organic matter pores in pyrobitumen of Longmaxi shale, with large diameter and strong connectivity, and solid kerogen had a little organic matter pores,while no organic matter pore was developed in pyrobitumen and solid kerogen of Niutitang shale. The two sets of shale have similar characteristics in total organic carbon content,whole rock mineral composition and kerogen type,but the thermal maturity of Niutitang shale is much higher than that of Longmaxi shale, and it has reached the metamorphism stage. The physical and chemical properties of solid kerogen and pyrobitumen tend to be similar to that of graphite, resulting in no pores developed in the organic matter. High thermal maturity is not conducive to the preservation of organic pores in shale, so the exploration and development of highover maturity marine shale gas of Lower Cambrian Niutitang Formation in southeastern Chongqing should focus on the area with thermal maturity less than 3.5%.