东濮凹陷地区东营组低熟原油地球化学特征及油源分析

Geochemical characteristics of crude oil and the analysis of oil sources of Dongying Formation in Wenliu area of Dongpu depression,China

对东濮凹陷文留地区东营组原油的族组分、饱和烃色谱特征和生物标志化合物等资料的分析,结果表明东营组含油砂岩抽提物饱和烃一般在50%左右、非烃+芳烃为50%、沥青质一般小于5%;饱和烃同位素变化范围为-27.3‰^-28.1‰,族组分之间的碳同位素分馏效应小;饱和烃色谱特征差别较大。这主要是与原油不同深度时生物降解作用的程度有关。甾萜烷系列中C27和C29重排甾烷含量低,重排甾烷/规则甾烷的比值在0.1左右,C2920S/(20S+20R)为0.2~0.4,三环萜烷、四环萜烷含量低,Ts大于Tm,奥利烷与γ蜡烷含量高,反映了高盐度沉积环境下形成的未熟-低熟油特征。油源对比结果显示文留地区西部沙河街组第三段源岩与东营组油藏具有较好的亲源关系。

This paper analyzes the group component, the saturated hydrocarbon chromatogram and the biomarkers of the crude oil of Paleogene Dongying Formation in the Wenliu area of the Dongpu depression and the results show that the extractable matter, that is, saturated hydrocarbon from the oil sand of Dongying Formation occupies about 50 %, and nonhydrocarbon and aromatic hydrocarbon occupies about 50%, and bitumen is usually 〈5%. The isotope of saturated hydrocarbon varies from -27.3‰ to -28.1‰ and the saturated hydrocarbon chromatogram differs greatly, because it haves something to do with the biodegradation degree of the crude oil in different depthes. The C27- and the C29- diasteranes of the sterane and terpane have a low content, and the ratio of diasterane and regular- sterane is about 0.1, and C29 20S/（20S＋20R） is between 0.2 and 0.4. The tricyclic and tetracyclic terpanes are low, and Ts is more than Tm. The oleanane and the γ-wax alkanes are high reflecting the feature of unmature or low-mature oil under sedimentary environments with a high salinity. The analysis of the oil source expresses the intimate relationship between the mudstone of Member 3 of Paleogene Shahejie Formation in the west of Wenliu and the oil pools of Dongying Formation.