东濮凹陷优质烃源岩生烃演化机理

复杂构造条件下蒸发成因咸化湖盆优质烃源岩的生烃演化机理,是目前有机地球化学研究最为关注的问题之一。为探索这一问题,文中以东濮凹陷为例,在分析烃源岩地球化学特征的基础上,开展了不同流体介质条件下优质烃源岩成烃生物组成和有限空间生烃热模拟等研究。结果表明:生烃过程受地层水矿化度和有机质生物来源的双重控制,咸水环境优质烃源岩最为发育,有机质来源于颗石藻、蓝藻和沟鞭藻等多种藻类的贡献,显微结构呈纹层状互层,生烃时间早,生烃周期长,液态烃产率高,具有5个生烃阶段;淡水环境优质烃源岩极少,有机质来源于绿藻和高等植物的贡献,生烃时间晚,液态烃产率低,气态烃产率高,仅具有3个生烃阶段;半咸水环境优质烃源岩的有机质主要来源于沟鞭藻,优质烃源岩发育概率、生烃时间、液态烃产率介于咸水环境和淡水环境烃源岩之间,具有3个生烃阶段。

Hydrocarbon evolution mechanism of high quality source rock in Dongpu Sag

Mechanism of evolution of hydrocarbon of high quality source rock in saline lacustrine basin caused by evaporation in complicated structural environment condition is currently one of the most concerned matters in organic geochemistry research.To explore this problem,based on source rock quality feature analysis,this paper takes the Dongpu Sag for example and carries out the thermal simulation of hydrocarbon generation in finite space and hydrocarbon-forming organisms of high quality source rock in fluid different medium conditions.The result shows that the hydrocarbon generation process is controlled by the salinity of formation water and the biological source of organic matter,and high quality source rock develops best in the saline environments.Hydrocarbon-forming organisms are mainly coccolith and blue-green algae.In microstructure,the main feature is interlamellar structure.Hydrocarbon generation time is early,hydrocarbon generation cycle is long,and liquid hydrocarbon yield is high.The hydrocarbon generation model has the feature of five-part form.In fresh water environment,the high quality source rock is relatively poor.Hydrocarbon-forming organisms are mainly green algae,and combined with large amount of advanced plant of terrestrial sources.Hydrocarbon generation time is late,liquid hydrocarbon generation rate is low,gas hydrocarbon generation rate is high,and the hydrocarbon generation model has the feature of three-part form.In brackish water environment,hydrocarbon-forming organisms of high quality source rock are of main dinoflagellates.The degree of development,hydrocarbon generation time and productivity of high quality source rock are between saline water and fresh water,whose hydrocarbon generation model is of three-part form.