不同类型煤系烃源岩对油气藏形成的作用

Contribution of various coal measures source rocks to oil and gas reservoir formation

以冀中坳陷东北部石炭二叠系和柴达木盆地北缘侏罗系主体煤系烃源岩为实例,运用油气地球化学新技术、新方法,在系统分析和总结大量烃源岩及油气样品(6629块/次)分析数据的基础上,根据油气源对比、不同类型烃源岩的综合评价和生烃量计算结果,确认冀中苏桥油气田的凝析油或轻质油主要是C2b—P1s含壳质组煤和炭质泥岩二次生排的油气;而柴北缘冷湖油田的原油主要来自J1浅湖—半深湖相泥岩,生排油气量也以湖相泥岩所生油气为主。煤系中的暗色泥岩、炭质泥岩和煤的有机质类型及显微组分随沉积相或亚相的变化而不同,生烃能力差别很大,滨海(湖)沼泽煤及炭质泥岩生烃能力多好于泥岩,而较深水—浅水湖(或海)沼泽泥岩生烃能力多优于煤。

New geochemical technologies and methods are used to study the main coal measures source rocks of Carboniferous- Permian Formations in NE Jizhong Depression and Jurassic Formations in the north margin of Qaidam Basin. The oil and gas source correlation, comprehensive evaluation and hydrocarbon generation quantitity calculation of various source rocks are studied by systemically summarizing the analysis data of source rocks and oil and gas samples （total 6629）. The results show that the condensate oils or light oils of Suqiao Oil/ Gas Fields in Jizhong Depression were mainly derived from the secondary hydrocarbon generation and expelling of the liptinite-bearing coals and carbonaceous mudstones of C2b-P1s Formations, while the oils of Lenghu Oilfield in the north margin of Qaidam Basin are mainly derived from the Lower Jurassic shallow-deep lake facies mudstones, and the generated and expelled oil and gas were also mainly from lake facies mudstones. The hydrocarbon generation abilities of dark mudstones, carbonaceous mudstones and coal in coal-bearing environments are quite different, and their organic matter types and macerals vary with the changing of sedimentary facies or sub-facies. The hydrocarbon generation abilities of coals and carbonaceous mudstones are better than those of dark mudstones when the coal measures source rocks deposited in littoral （lake） paludal facies, whereas the hydrocarbon generation abilities of dark mudstones are better than those of coals when the coal measures source rocks deposited in deep-shallow lake （or marine） paludal facies.