Research on the source rock types and thermal evolution of the Permian Lower Wuerhe Formation in the Shawan Sag,Junggar Basin
The lower play in Shawan Sag is rich in oil and gas resources,and the Lower Wuerhe Formation has been proven to be the main source rock.However,the thermal evolution and hydrocarbon generation history of the source rock have not been clearly understood due to the deep burial and low research degree,which limits the understanding of the hydrocarbon migration and accumulation in lower play.Based on geochemistry data of source rock,the basic characteristic of the source rock is analyzed,and the thermal evolution and hydrocarbon generation history of the Lower Wuerhe Formation are reconstructed by basin modeling,and then the hydrocarbon accumulation process is preliminarily analyzed.The results show that the source rocks of the Lower Wuerhe Formation in the Shawan Sag are mainly Type Ⅱ organic matter,with an average organic carbon content of 0.82%and a potential hydrocarbon generation of 5.32 mg/g,which are medium source rocks.The current maturity is approximately 1.27%and they are in the mature to highly mature stage.The result of thermal evolution simulation shows that the source rocks entered the threshold of hydrocarbon generation(Ro = 0.5%)since the Late Triassic and reached the peak of oil generation(Ro = 1.0%)in the Jurassic-Late Cretaceous.After the end of the Cretaceous,the thermal evolution of organic matter entered a high maturity stage(Ro＞1.3%)and the kerogen was cracked to produce wet gas.The ultra-deep reservoir experiences multi-stage oil and gas charge,multi-stage mixed oil and gas charge and the fault differential activity result in the coexistence of multi-phase oil and gas reservoirs in different formations in the Shawan Sag.The research and understanding have established a strong basis for comprehending the mechanisms and procedures involved in the ultra-deep hydrocarbon accumulation within the Junggar Basin.
Source rockThermal evolutionHydrocarbon generation historyBasin modelingShawan Sag
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