准噶尔盆地沙湾凹陷二叠系下乌尔禾组烃源岩类型与热演化研究

沙湾凹陷下组合油气资源丰富，下乌尔禾组烃源岩被证实是凹陷内主要的油气来源。然而，由于烃源岩埋深较大、勘探程度低，烃源岩类型、热演化以及生烃史尚不清楚，制约了下组合油气成藏规律的认识。本研究基于烃源岩地球化学参数，认识下乌尔禾组烃源岩基本特征，利用盆地模拟恢复烃源岩热演化以及生烃演化史，在此基础上对油气成藏过程进行分析。结果表明：沙湾凹陷下乌尔禾组烃源岩有机质类型以Ⅱ型为主，平均有机碳含量（TOC）为0.82%，生烃潜量（S₁+S₂）为5.32 mg/g，为中等烃源岩，平均成熟度（R_o）为1.27%，处于成熟—高成熟阶段。热演化模拟显示下乌尔禾组烃源岩于晚三叠世晚期进入生烃门限（R_o=0.5%），晚侏罗世—晚白垩世达到生油高峰（R_o=1.0%）。白垩纪末期，有机质热演化进入了高成熟演化阶段（R_o＞1.3%）。沙湾凹陷超深层储层经历多期油气充注，油气的多期混合以及断层活动的不均一性造成不同层位多种相态油气藏共存。研究认识为准噶尔盆地超深层油气成藏过程和机理研究奠定了坚实的基础。

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.