塔中地区下奥陶统油气地球化学特征及成因  

Geochemical Characteristics and Origin of Hydrocarbons from Lower Ordovician in Tazhong Area,Tarim Basin

作　　者：李素梅[1,2] 肖中尧[3] 吕修祥[1,2] 张宝收[3] 张海祖[3] 

机构地区：[1]中国石油大学油气资源与探测国家重点实验室,北京102249 [2]中国石油大学地球科学院,北京102249 [3]中国石油塔里木油田分公司勘探开发研究院,新疆库尔勒841000

出　　处：《新疆石油地质》2011年第3期272-276,共5页Xinjiang Petroleum Geology

基　　金：国家"973"基金项目(2006CB202308);国家自然科学基金项目(40973031)

摘　　要：通过多种地球化学分析方法,对塔中地区下奥陶统油气地球化学特征与成因进行详细研究,结果表明,下奥陶统原油是以低分子量轻质馏分为主、生物标志物含量极低的高-过成熟原油,以芳烃中含有高-超高丰度的含硫芳烃-二苯并噻吩(DTBs)而显著不同于中上奥陶统等上部层系。依据单体烃碳同位素特征,结合烃类组成与分布,认为下奥陶统原油为来自寒武系-下奥陶统和中上奥陶统的混源油,前者的贡献总体高于后者。下奥陶统原油中较高丰度的硫醇化合物、丰富的四氢噻烷、高含量H2S(近10%)伴生气以及超高丰度的含硫芳烃的存在,表明其经历了硫酸盐热化学还原作用、热化学作用等复杂的油气成藏后作用,这些作用改造了油气藏中的烃类并对油气藏的保存可能产生重要的影响。Multiple approaches are applied to analysis of the characteristics and origin of the oils from the Lower Ordovician in Tazhong area,Tarim basin.The results show that the oils are primarily condensate oil featured by dominant fractions with low molecular weight and much low content of biomarkers such as steroids and terpenoids,suggesting high-overmature crude oils.It is distinguished from that of the overlying Middle-Upper Ordovician by particularly high-super high dibenzothiophene in aromatics.It is suggested that most of the Lower Ordovician oils are mixed-source oils from both the Cambrian-Lower Ordovician and the Middle-Upper Ordovician with a little higher contribution of the former based on chemical compositions of hydrocarbons and compound-specific carbon isotope of n-alkanes in the oils.It is detected that the Lower Ordovician oils are enriched in mercaptan and long chain alkyl thiolanes.These features together with high H2S content in associated gas as well as high dibenzothiophene in the oils indicate that hydrocarbons from the Lower Ordovician should have suffered some alterations such as thermochemical sulphate reduction（TSR） after accumulation to a certain degree.These might have played an essential role in hydrocarbons alteration and reservoir preservation in this area.

关 键 词：塔里木盆地 塔中隆起 下奥陶统 生物标志物 同位素 油源 硫酸盐热化学还原作用 

分 类 号：TE112.111[石油与天然气工程—油气勘探]