准噶尔盆地吉木萨尔凹陷中二叠统芦草沟组致密油藏原油物性具有“四高”(较高密度、较高黏度、较高凝固点和较高含蜡量)特征,饱和烃色谱研究表明,原油的正构烷烃分布完整,未遭受生物降解作用;轻烃和甾烷成熟度指标反映,原油整体处于低成熟演化阶段,与芦草沟组烃源岩热演化阶段一致,具有近乎一致的地球化学指纹特征,表明二者具有良好的亲缘性,具“源储一体”的致密油藏成藏特征.通过生烃模拟实验发现,芦草沟组烃源岩在低成熟阶段的累计生、排烃量和排油率,相当于正常烃源岩在成熟阶段的生、排烃量和排油率.半深湖-深湖相沉积、咸化的还原-强还原环境以及优良的生烃母质(Ⅰ型-Ⅱ型干酪根),是吉木萨尔凹陷芦草沟组优质烃源岩早期大量生烃、排烃和形成低成熟致密油藏的主要原因.%The tight oil reservoir of Middle Permian Lucaogou formation in Jimsar sag,Junggar basin has characteristics of "4-high" physical properties (i.e.relatively high density,high viscosity,high pour point and high wax content).The study on saturated hydrocarbon chromatography shows that the distribution of n-alkanes in the crude oil is complete and the crude oil never suffered from biodegradation;the maturity indexes of light hydrocarbons and sterane demonstrate that the oil is in the low maturity stage.The oil and source rocks in Lucaogou formation show the same thermal evolution stage and geochemical fingerprint characteristics,indicating a good affinity between them and tight-oil reservoir forming characteristics of "source and reservoir integration".The oil generation simulation experiment shows that the accumulative hydrocarbon generation and expulsion quantities and oil discharge rate of the source rocks in Lucaogou formation at low mature stage are almost the same with those of normal source rocks at mature stage.Half-deep and deep lacustrine facies sediments,salinized reducing-strong reducing environments and good parent materials of hydrocarbons (Type Ⅰ-Ⅱ kerogens) are the main causes for large quantities of hydrocarbon generation and expulsion,and low-maturity tight oil accumulation of the good-quality source rocks in Lucaogou formation of Jimsar sag at the early stage.
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