松辽盆地双城——太平川地区原油地球化学特征及其成熟度差异

松辽盆地北部双城—太平川地区扶杨油层原油地球化学特征相近,正构烷烃分布完整,呈单峰型,主峰碳主要为C23,部分原油具有轻碳优势,奇偶优势不明显。三环萜烷含量较丰富,部分原油伽马蜡烷、孕甾烷和升孕甾烷含量较高,规则甾烷呈"V"型分布,碳同位素值偏轻,生源构成以低等水生生物和菌藻类为主,兼有高等植物生源输入,母源形成环境为微咸水还原—淡水氧化环境。本区原油的总体特征比较接近,具有相似的生源母质和有机相,但其成熟度存在着一定差异。根据生物标志物参数,原油分为三个组群,即低成熟油、低成熟—中等成熟油和中等成熟油,主要为低成熟—中等成熟原油。认为研究区具有形成低成熟油的有利烃源条件,应该加强对低成熟油的勘探开发。同时加强长春岭背斜带及其周缘构造高部位有利圈闭的勘探与评价。

Geochemical Characteristics and Maturity Difference of Crude Oil from Shuangcheng-Taipingchuan Area in Songliao Basin

A great petroleum exploration potential exists in Shuangcheng-Taipingchuan area in Songliao Basin. Ana- lyzed crude oils from Fuyu-Yangdachengzi oil layers have similar geochemical characteristics. The distribution of n- alkane plots is complete and show single peaks with the main peak carbon of C23, unconspicuous odd-even predomi- nance in which parts of crude oils are light carbon predominance. The characteristics of biomarkers are: (1) relative high contents of tricyclic terpane, (2) relative high contents of gammacerane, pregnane and homopregnane, (3) V- shaped distribution of regular sterane. The carbon isotope value is generally small. It is demonstrated that the biolog- ical sources of crude oil would mainly be composed of low-grade aquatic organism and thallophyta as well as higher planet, and the source rocks would had been deposited in brackish water reducing-fresh water oxidated environment. These crude oils have similar characteristics in generally and have similar biological sources and organic facies but some differences exist in thermal maturity of these crude oils. According to biomarker parameters, the crude oils are divided into three families: low thermal maturity oil, low-middle thermal maturity oil and middle thermal maturity oil, a- mong which low-middle thermal maturity oils are common. It is suggested that an attention should be paid to the area of low thermal maturity oil favorable for exploration.