泥质烃源岩中不同赋存状态有机质定量表征——以东营凹陷沙河街组为例

Quantitative Characterization of Organic Matters with Different Occurrences in Argillaceous Source Rocks: A Case of Shahejie Formation, Dongying Sag

泥质烃源岩中的滞留有机质存在多种赋存状态,包括游离态有机质和矿物结合态有机质。不同赋存状态有机质的性质存在较大差别,故而在烃源岩精细评价中的意义不同,但尚无完善的对其定量表征的方法。采用东营凹陷沙三段中亚段、沙三段下亚段和沙四段上亚段泥质烃源岩黏粒级样品,通过分析溶剂抽提和连续化学处理过程中(碱解-HCl酸解-HF/HCl酸解处理)样品热解参数的变化,包括游离烃、裂解烃和总有机碳含量等参数的变化规律,以及定量测定不同赋存状态有机质的产率,建立了不同赋存状态滞留有机质的定量表征方法。研究结果表明,矿物结合态可溶有机质在烃源岩滞留有机质中的数量十分可观,传统地化分析中的Rock-Eval热解评价方法和氯仿沥青A评价方法评价烃源岩生烃潜力存在较大局限性。深入研究矿物结合态有机质的地化特征,将会拓宽对油气生成理论及滞留油气赋存状态的认知。

The organic matters retained in argillaceous source rocks are of various occurrences, including free state and mineral-bindingstate organic matters which have quite different geochemical natures and different significance in detailed source rock evaluation. However,a comprehensive quantitative characterization technique for both occurrences has not been established yet. With the argillaceous sourcerocks sampled from the middle Es3, the lower Es3 and the upper Es4 of the Shahejie formation, Dongying sag, and based on the analysis onthe changes of pyrolysis parameters during the processes of solvent extraction and sequential chemical treatment including the variations offree hydrocarbon, cracked hydrocarbon and TOC, the paper measures the abundance of the organic matters with different occurrences quan-titatively and establishes a quantitative characterization method of retained organic matters with different occurrences. The results showthat the quantity of soluble organic matters of mineral-binding state is quite large in the organic matters retained in source rocks. Tradition-al evaluation methods such as Rock-Eval pyrolysis method and chloroform bitumen A method have some limitations. Profound study on thegeochemical characteristics of the organic matters of mineral-binding state will widen the knowledge of hydrocarbon generation theory andretained hydrocarbon occurrences.