东海盆地X凹陷烃源岩生烃特征

Hydrocarbon generating Characteristics of Source Rocks in a Seg of East China Sea Basin

采用有机岩石学和有机地球化学相结合的方法，系统研究了东海盆地Ｘ凹陷下第三系烃源岩生烃母质、原油化学组成与油源、有机质热演化与生烃模式。该区烃源岩（煤和泥岩）富含树脂体（全岩平均含量达４％，相对含量占１５％～５０％），且树脂体含量与烃源岩总烃含量呈密切的正相关性。光学显微镜下，烃源岩中发现大量由树脂体母体衍生的渗出沥青体，表明了树脂体的早期生烃。花港组轻质原油源自同组的泥岩，均具有树脂生源成因的烃类组成特征。利用镜质组反射率、孢子体荧光变化，可将该区烃源岩有机质热演化划分为４个演化阶段。在此基础上，初步建立了该区烃源岩生烃模式，即以树脂体为主要母质的低熟油生成带（Ｒｏ＜０．５５％）和以孢子体、藻类体等富氢组分为代表的常规成熟油气生成带（Ｒｏ为０．５５％～１．３０％）。

A systematical study on hydrocarbon generating materials of paleogene source rocks,chemical composition and origin of crude oil,organic matter thermal evolution and hydrocarbon generation model in X sag,East China Sea basin is made by using a comprehensive method of organic petrology and organic geochemistry In the source rocks(coal and mudstone) of X sag,resinite is rich with an average content of 4% in the whole rock volume and a relative content of 15 50% There is a close positive correlation between resinite and total hydrocarbon contents in the source rocks A large amount of exsudatinites derived directly from their parent resinite bodies are found in the source rocks under optical microscope(R o <0 7%) All these features indicate the early hydrocarbon generation of resinite The light crude oil in the Huagang formation originates from the mudstone in the same formation,both the oil and mudstone are characterized by the hydrocarbon composition of resin genetic source According to changes in vitrinite reflectance and fluorescence parameters (λ max ,Q and I 546 ) of sporinite,the organic evolution process of X sag can be divided into stages Ⅰ,Ⅱ,Ⅲ and Ⅳ Based on the above study,a geochemical hydrocarbon generation model for X sag is proposed,in which there are two oil generating zones:an immature oil generation zone from resinite (R o <0 55%) and a conventional mature oil and gas generating zone from sporinite and alginite (R o =0 55-1 30%)。