安塞地区长10段原油地球化学特征及油源探讨

通过对安塞油田G52井长10段原油样品的地球化学分析,系统地研究了原油的分子标志化合物的分布特征,并且进行了油源对比.研究结果表明,长10段原油饱和烃中以低碳数正构烷烃分布为主,呈单峰态分布,主峰碳为nC21,无明显奇偶优势,规则甾烷中ααα20RC27,C28,C29呈"L"型分布,ββ构型甾烷丰度较高.萜烷系列中三环萜烷的丰度中等,五环三萜类中Ts,C29Ts以及18a(H)-重排藿烷的丰度明显偏高,伽马蜡烷指数较低,而常规的升藿烷系列化合物丰度不高,明显受成熟度的影响.由此表明长10段原油主要来源于淡水或微咸水的弱氧化-还原环境,是以低等水生生物或藻类输入为主的湖相烃源岩,而且已经达到高成熟阶段.G52井长10段与长6—长9段原油和研究区烃源岩生标分布以及相关参数对比表明,长10段原油与长9段烃源岩生物标志化合物特征具有相似性,初步认为长10段原油主要来自长9段烃源岩.

Study on the geo-chemical characteristics and the oil source of Chang 10 member oil in Ansai oilfield

Based on the analysis of the geo-chemical characteristics of the oil samples collected from Chang 10 member of G52 well in Ansai oilfield,the distribution characteristic of the biomarkers and the oil source of the samples are systematically studied.The results show that n-alkane of the oil samples is characterized by unimodal distribution without even or odd n-alkanes predominance,and main carbon peak is at nC21.The distribution C27∶C28∶C29 ααα20R steranes presents "L" shaped,and ββ-steranes has high abundance.The abundance of tricyclic terpane is medium,and Ts,C29Ts and 18a(H)-rearranged hopanes have higher abundance and lower gammacerane index.The lower abundance of C31-C35 homohopanes indicates that the oil has high maturity.The compositions and parameters of the biomarkers indicate that the mature crude oil is generated from the lacustrine source rock mainly enclusing lower hydrobionts and lacustrine algaes under the environments of fresh-brackish lacustrine.According to the comparison of the distribution and related parameters of the biomarkers in Chang 10 crude oil with those in the hydrocarbon source rock of Chang 6-Chang 9,it is shown that the characteristics of the biomarkers in Chang 10 crude oil is similar to those in Chang 9 hydrocarbon source rock,so it is held that the Chang 10 crude oil is mainly from the Chang 9 hydrocarbon source rock.