准噶尔盆地沙湾凹陷原油地球化学特征与油源分析

Geochemical Characteristics and Source of Crude Oil in Shawan Depression,Junggar Basin

沙湾凹陷作为准噶尔盆地西北缘重要的油气富集凹陷,在红车断裂带和斜坡区域均有重大油气发现。为明确沙湾凹陷周缘构造原油的来源,采用全烃地球化学分析方法,分析准噶尔盆地西北缘地区4套烃源岩和原油的地球化学特征,进行油-源和油-油对比研究。研究认为沙湾凹陷原油可分为5类,5类原油生物标志化合物指标与碳同位素分别表现为不同的特征,其中:A_(1)亚类原油来源于二叠系下乌尔禾组烃源岩高成熟阶段,A_(2)亚类原油来源于下乌尔禾组烃源岩成熟阶段,B类原油来源于风城组和下乌尔禾组的烃源岩的混合,C类原油来源于二叠系风城组烃源岩成熟—高成熟阶段,D类原油为侏罗系烃源岩产物。

As an important oil and gas enrichment depression in the northwestern margin of Junggar basin,Shawan depression has significant oil and gas discoveries in Hongche fault zone and slope area.In order to clarify the source of crude oil in the structural periphery of Shawan depression,the geochemical indexes of four sets of hydrocarbon source rocks and crude oil in the northwestern margin of Junggar basin were analyzed,and the oil-source correlation was studied using the whole-hydrocarbon geochemistry.It is believed that the crude oil in Shawan depression can be divided into five types with different characteristics in biomarkers and carbon isotopes.Based on the geochemical characteristics of each set of hydrocarbon source rocks,it is considered that the Subtype A_(1) of crude oil in Shawan depression origins from the high matured source rocks of the Xiawuerhe Formation of Permian,the Subtype A_(2) of crude oil comes from the normal matured source rocks of the Xiawuerhe Formation,the Type B of crude oil derives from the intermixture of the products of the source rocks of the Fengcheng Formation and the Xiawuerhe Formation,the Type C of crude oil originates from the normal to high matured source rocks of the Fengcheng Formation of Permian,and the Type D of crude oil are the product of the Jurassic source rocks.