页岩纳米级孔隙在有机质熟化过程中的演化特征及影响因素

有机质热演化程度是控制页岩纳米级孔隙形成演化的主要因素之一。利用室内含水封闭热解系统对松辽盆地长岭凹陷嫩江组二段湖相页岩开展了生烃全过程模拟实验（R_o=0.61%~4.01%），并对处于不同热演化阶段的样品进行了索氏抽提，基于抽提前后有机碳含量、N₂吸附和矿物组成等地球化学分析结果，研究了有机质成熟过程中纳米级孔隙形成演化特征及影响因素。页岩在模拟实验后BJH孔体积和BET比表面积均大幅增加，其变化范围分别为0.006 73~0.101 61 cm3/g和0.60~15.75 m2/g。成熟-高熟阶段干酪根热降解和残留烃热裂解促使纳米级孔隙快速发育，过熟阶段随着有机质生烃能力减弱，纳米级孔隙发育速率变缓；生油高峰期液态烃生成并充注在纳米级孔隙内，抑制了纳米级孔隙形成。油气生成和排出过程对纳米级孔隙发育起主导作用，固体焦沥青在不断富集的同时其本身发育纳米级有机孔隙，黏土矿物的伊利石化和石英溶蚀均有利于纳米级孔隙发育。 

Evolution characteristics and controls of shale nanopores during thermal maturation of organic matter

Organic maturity is one of the main factors controlling the formation and evolution of nanopores in shale. The whole process of hydrocarbon generation was modeled for lacustrine shale in the 2nd member of Nenjiang Formation in the Changling Sag of Songliao Basin by using hydrous pyrolysis experiments in a closed system (R_o=0.61%-4.01%). Shale samples at different thermal evolution stages were solvent extracted. Based on geochemical analysis results of organic carbon content, N₂ adsorption and mineral composition, the formation and evolution characteristics and influencing factors of nanopores during thermal maturity of organic matter were systematically studied. The BJH pore volume and BET specific surface area of shale increase greatly after pyrolysis experiments, and the variation ranges are 0.006 73-0.101 61 cm3/g and 0.60-15.75 m2/g, respectively. Thermal degradation of kerogen and cracking of residual hydrocarbons promote the rapid development of nanopores in the mature to high maturity stage, and growth rate of nanopores slows down with weakening of hydrocarbon generation ability of organic matter in the over-mature stage. Liquid hydrocarbon is generated and fills nanopores during peak oil generation, which inhibits the formation of nanopores. Generation and expulsion of oil and gas play a leading role in development of nanopores. Organic nanopores may develop while solid pyrobitumen continuously enriched. Illitization of clay minerals and quartz dissolution are conducive to the development of nanopores.