Evolution Character And Generating And Expelling Hydrocarbon Modeling Of Marine Sourse Rock Of Lower Assemblage In Southern Key Area

Southern marine lower assemblage (Sinian-Palaeozoic) is an important oil and gas exploration filed.The researched area including northeastern Sichuan-cengtral Guizhou, western Hubei-eastern Chongqin and their surrounding areas can be divided into seven districts: eastern Sichuan, western Hubei, eastern Henan, southern Guizhou, northern Sichuan, northeastern Guizhou, northern Guizhou, cengtral Guizhou and northwestern Hunan.Based on the analysis of paleo-sendimentary environment of forming source rockes, effective source rocks strata and their organic matter abundance and types, through organic petrology and geochemistry, and the burial history and thermal evolution of these seven districts, maturity evolution history and generating&expelling hydrocarbon(GEH) history of these source rocks will be stimulated by BasinMod software, furthermore, GEH periods will be classified and then advantageous GEH area will be given.Most of the Lower Assemblage source rocks are at an over-mature dry gas stage, while some of them are at the high mature wet gas advanced stage.The results of the simulation of burial history, thermal matural history and GEH show that the Lower Assemblage source rocks evolution are effected by the deposition occurred in Cambrian-Silurian, Permian-Triassic and Jurassic-Cretaceous.So there are 3 periods of generating and expelling hydrocarbon:middle to late Caledonian epoch, Indo-Chinese epoch and early to middle Yanshanian epoch.The time of entering"oil window"and"gas window"in southern area(including southern and southeastern Guizhou) is earlier than in northern area, Sinian-Cambrian source rocks exhausted in the early Hercynian-Indo-Chinese epoch, and silurian source rocks also began to exhaust in the Indo-Chinese epoch;Sinian-Cambrian source rocks in most area of middle and north(including eastern Sichuang, northern Guizhou-southern Sichuang) exhausted in the early-middle Yanshanian epoch, meanwhile silurian source rocks were in the hydrocarbon generating peak but stopped due to tectonic uplifting;Sinian-Cambrian source rocks exhausted in the western Hubei-eastern Chongqing and west Hunan exhausted in the early Hercynian-Indo-Chinese epoch, and silurian source rocks stop generating hydrocarbon just after entering"gas window"because of tectonic uplifting;evolution of source rocks in the cengtral Guizhou were delayed because of sedimentary strata uplifting dramatically, and so far Sinian to lower-Cambrian source rocks still have potential in generating hydrocarbon in the middle Yanshanian but stopped due to tectonic uplifting.GEH stimulation experiments respect generation and distribution characteristics of high and over mature marine source rocks by generating hydrocarbon, expelling hydrocarbon efficiency of source rocks, and substance component and phase transform.The source rocks of researched area are in the period of dry gas evolution, and generate gas only.Tmax increase by degrees slowly and generating hydrocarbon efficiency rise very slowly.In the process of generating hydrocarbon, pyrolysis of the generated hydrocarbon occurred and kerogen generating potential exhausted gradually, and gaseity hydrocarbon came from pyrolysis of the heavy one mainly, instead of high evolution kerogen itself.The organic matter of source rocks in southern lower assemblage still have about 5% generating hydrocarbon potential after reaching dry gas evolution period, referring to GEH efficiency of the compared samples of source rocks.