鄂尔多斯盆地吴起地区长9段和长10段原油地球化学特征对比  

Comparative study on geochemical characteristics of Chang 9 and Chang 10 crude oils in the Wuqi Oilfield,Ordos Basin

作　　者：王钊[1,2] 周新平 李树同[1] 李士祥[3] 邱军利[1] 张文选[3] 王琪[1] 

机构地区：[1]甘肃省油气资源研究重点实验室/中国科学院油气资源研究重点实验室,甘肃兰州730000 [2]中国科学院大学,北京100049 [3]中国石油长庆油田分公司勘探开发研究院,陕西西安710018

出　　处：《天然气地球科学》2017年第9期1385-1395,共11页Natural Gas Geoscience

基　　金：国家科技重大专项"大型油气田及煤层气开发"(编号:2016ZX05007-004)资助

摘　　要：鄂尔多斯盆地吴起地区延长组长9油层组和长10油层组的源储特征存在较大争议。针对这一问题,通过地球化学测定方法,对该地区长9段原油和长10段原油的地球化学特征进行了精细对比和解剖,研究发现:长9段原油地球化学特征变化较大,其正构烷烃具有双峰和单峰2种类型,C_(27)—C_(29)甾烷呈倒"L"型分布,表现出明显的高等植物输入特征,说明母质来源广泛。长10段原油正构烷烃呈单峰分布,C_(27)—C_(29)甾烷呈"V"型分布,母质来源基本上均为水生微生物,并且来源集中。结合碳同位素特征判断长9段—长10段原油形成于淡水弱还原—弱氧化环境中。综合以上特征推断出长9段原油和长10段原油可来源于不同的烃源岩。它们具有完全不同、相对独立的油源。长9段原油部分来自长7段上部烃源岩。该发现将为延长组下组合的成藏机理研究提供帮助。There are great disputes about the source and reservoir characteristics of Chang 9 oil-bearing for- mation and Chang 10 oil-bearing formation in Yanchang Formation, Ordos Basin.Aiming at this problem, the geochemical characteristics of crude oil in Chang 9 reservoirs and Chang 10 reservoirs were finely con- trasted and dissected.The study showed that geochemical characteristics of crude oil in Chang 9 reservoir ranged obviously.The distribution of n-alkanes resented two types： Single-peak or double-peak carve; The structure of the sterane is reversed ＂L＂ type distribution,which showed obvious characteristics of higher plant input,indicating a wide range of parent material;The distribution of n-alkanes in Changl0 reservoir showed single-peak distribution.The structure of the sterane is ＂V＂ type distribution, showing the sources of parent material were mainly aquatic microorganisms,and the sources were relatively concentrated.Com- bined with carbon isotope characteristics, it can be judged that the Chang 9-Chang 10 crude oils were formed in the weak reductive weak oxidation environment with fresh water.Based on the above characteris- tics,it is concluded that the crude oil of Chang 9 and Chang 10 can be derived from different source rocks. They have completely different and relatively independent source reservoir characteristics.Chang 9 crude oil was partly sourced from the upper part of Chang 7 source rock,which will be helpful to the study of reser- voir forming mechanism in the lower Yanchang Formation.

关 键 词：原油 地球化学特征 甾烷 藿烷 母质来源 沉积环境 油源 

分 类 号：TE122.113[石油与天然气工程—油气勘探]