黔南坳陷下石炭统摆佐组暗色页岩热演化与生烃史研究

摘要

The thermal evolution and hydrocarbon generation histories of the Lower Carboniferous Baizuo Forma-tion in the Southern Guizhou Depression were studied with petroleum geology, geochemical data and petroleum system simulation in order to evaluate the hydrocarbon generation potential of black shale.Results showed that the black shale of the Baizuo Formation has relatively high organic matter abundance and low hydrocarbon potential. The organic matter in the black shale is mainly of type Ⅱ2,and has reached the high-maturity and over-mature stages. The black shale entered the threshold of hydrocarbon generation during the Middle Carboniferous(about 312 Ma)and the mature stage in the early Triassic(about 238 Ma), and reached the maximum burial depth (about 9 000 m)in the early Jurassic(196 Ma),with a maximum temperature of about 200 ℃. They reached the oil generation peak in the Middle Permian(291-270 Ma)and the gas generation peak in the Late Triassic (262-208 Ma),respectively. The process of oil cracking to gas during the high thermal evolution provided suffi-cient methane gas and storage space for shale gas enrichment. However,tectonic uplift and erosion since 196 Ma had a certain destructive influence on shale gas enrichment.%为了对黔南坳陷下石炭统摆佐组暗色页岩的生烃能力进行评估,利用油气地质、地球化学资料分析以及含油气系统模拟技术等方法,对其热演化—成熟历史和生烃演化的过程进行了重建.研究表明:摆佐组页岩具有较高的有机质丰度和较低的生烃潜量,有机质类型主要为Ⅱ2型,已经达到高—过成熟阶段;摆佐组页岩从中石炭世(约312 Ma)开始进入生烃门限,在早三叠世(约238 Ma)进入过成熟阶段,在早侏罗世(约196 Ma)达到最大埋深9000 m,最高温度约为200℃;摆佐组页岩分别在二叠纪中期(291~270 Ma)和三叠纪后期(262~208 Ma)达到生油和生气高峰;高演化背景下的油裂解气过程,可为摆佐组页岩气的富集提供充足的甲烷气和存储空间,然而196 Ma以来的构造抬升剥蚀对页岩气的保存具有一定的破坏作用.