东营凹陷王家岗地区原油地球化学特征及成因类型

通过对研究区原油、含油砂岩和烃源岩样品抽提物中饱和烃和芳香烃化合物的地球化学特征对比分析, 将该区原油划分为4 种成因类型。第1类原油低密度、低含硫量、高含蜡量、饱和烃碳数分布呈“单峰型”、植烷优势[m(Pr)/m(Ph) 为0.51~0.72) ] 、规则甾烷相对含量C₂₉>C₂₇>C₂₈呈反“L”型, 反映了以高等植物生源为主的特征, 成熟度高, 来源于孔二段烃源岩; 第2类原油高密度、高含硫量、低含蜡量、“单峰型”、异常高植烷含量[m(Pr) /m(Ph) <1.0]、规则甾烷C₂₉>C₂₇>C₂₈呈不对称“V”型、高伽马蜡烷含量, 反映了咸水低等水生生物来源, 成熟度较低, 为沙四段烃源岩生成原油; 第3 类原油饱和烃呈“双峰型”, 规则甾烷C₂₉>C₂₇>C₂₈也呈反“L”型, 反映了低等水生生物与高等陆源植物混合来源的特征, 来源于孔二段和沙四段烃源岩; 第4类原油遭受生物降解, 正构烷烃缺失, 为孔店组和沙四段形成的混源油或沙四段原油。该区4类原油在空间上呈规律性分布。

Geochemical Characteristics and Origin Classification of Crude Oil in Wangjiagang Area in Dongying Sag

The correlation of geochemical characteristics of saturated hydrocarbon and aromatic hydrocarbon compounds among crude oil,oil-bearing sandstone and source rock extractive matters in the studied area is conducted.The result shows that the crude oil can be divided into four types of origins.The first type of crude oil is characterized by low density,low sulfur,high wax content,gas chromatography of saturated hydrocarbon showing single peak,m(Pr)/m(Ph) ratio ranging from 0.51 to 0.72,relative content of sterane of C29>C27>C28 showing reverse "L" shape and high maturity,reflecting the origin of higher plants,which originates from Ek2 source rock;the second type by high density,high sulfur,low wax content,single peak shape,m(Pr)/m(Ph) ratio less than 1.0,sterane content of C27>C29>C28 showing asymmetrical "V" shape,high gammacerane content and high maturity,reflecting the origin of lower aquatic organism,which originates from Es4 source rock;the third type shows dual-peak shape,sterane content of C29>C27>C28 also showing reverse "L" shape,reflecting the mixed origin of lower aquatic organism and higher terrigenous plants,which originates from Ek2 and Es4;the fourth type by biodegradation and lack of n-alkane,being an origin-mixed crude oil of Es4.The fourth types of crude oils in this area assume regular distribution spatially.