澳大利亚波拿巴盆地Petrel次盆古生界页岩有机质热演化的差异及其地质意义

Thermal evolution differences and its geological significances of organic matter of Paleozoic shale in Petrel subbasin,Bonaparte Basin,Australia

通过地质、地球物理、地球化学资料分析以及含油气系统模拟技术,对澳大利亚波拿巴盆地Petrel次盆未钻或少钻区域古生界3套页岩有机质演化过程进行研究。结果表明:二叠纪是石炭系页岩气生成的高峰期,二叠纪中-晚期可能是原油二次裂解气生成的高峰期,侏罗纪至今是石炭系Milliigans组页岩气的破坏期,现今页岩层内保存的天然气可能较为有限;侏罗纪是下二叠统Keyling组页岩气生成的高峰期;第三纪以来上二叠统Hyland Bay组页岩一直处于生气高峰期,新近纪至今可能是其原油二次裂解气生成的高峰期。受区域差异沉降的控制和影响,Petrel次盆中-北部烃源岩埋深大,有机质演化程度高,东-西部烃源岩埋深小,热演化程度相对较低。

Combining comprehensive analyses of geological,geophysical and geochemical data and modeling using petroleum system modeling technology,this study tries to restore the evolution processes of organic matter in three sets of Paleozoic shales with no or little drilling data in Petrel subbasin of Bonaparte Basin in Australia.The results show that the entire Permian is the generation peak of Carboniferous shale gas,and the Middle and Late Permian may be the generation peak of oil cracking gas.The shale gas in the Carboniferous Milliigans formation may have been under destruction since the Jurassic,leaving presently limited gas in the shale.The Jurassic is the generation peak of shale gas in the Permian Keyling formation.The shale of Hyland Bay formation in the upper Permian has been at gas generation peak since the Tertiary,and the period since the late Tertiary may be the generation peak of oil cracking gas.Controlled and influenced by regional differential settlement,the source rocks in the middle and north part of Petrel subbasin are deeper with a relatively high degree of organic evolution,while in the east and west part of the basin the rocks are shallower with a relatively low degree of thermal evolution.