塔里木盆地顺北油气田不同层系原油地球化学特征对比及成因分析  

Geochemical characteristics and origin of oil from different strata in Shunbei oil and gas field, Tarim Basin

作　　者：罗明霞[1] 夏永涛[1] 邵小明[1] 吴鲜[1] LUO Mingxia;XIA Yongtao;SHAO Xiaoming;WU Xian(Exploration and Production Research Institute of Northwest Oilfield Branch,SINOPEC,Urumqi,Xinjiang 830011,China)

机构地区：[1]中国石化西北油田分公司勘探开发研究院

出　　处：《石油实验地质》2019年第6期849-854,共6页Petroleum Geology & Experiment

基　　金：国家科技重大专项“塔里木—鄂尔多斯盆地海相碳酸盐岩层系大中型油气田形成规律与勘探评价”(2017ZX05005-002)资助

摘　　要：塔里木盆地顺北油气田在奥陶系、志留系和白垩系多个层系都可见挥发油—轻质油或油砂。通过地球化学特征对比发现,不同层系的原油(油砂)存在较大差异。根据其成因总体上可以划分为2类:(1)奥陶系和志留系:姥植比较低(Pr/Ph<1),原油族组分及正构烷烃单体烃类的碳同位素偏轻,三环萜烷C21TT/C23 TT比值小于1.0,三芴含量中硫芴占绝对优势,均表现为海相腐泥型原油,但两者成熟度略有差异,志留系为成熟油,奥陶系为高熟油;(2)白垩系:姥植比较高(Pr/Ph>1.6),原油碳同位素相对较重,C21TT/C23TT比值大于1.0,C24四环萜烷及C30重排藿烷相对丰度高,表现为陆相原油特征。综合分析,志留系及奥陶系原油来自寒武系烃源岩,为同源不同期的油藏,而白垩系原油可能来自北部库车坳陷陆相烃源岩。Volatile-light oil or oil sands have been found in the Ordovician,Silurian and Cretaceous strata in Shunbei oil and gas field,Tarim Basin.The geochemical characteristics of oil or oil sands from these strata are obviously different.Generally,they can be divided into two genetic types.(1)Oil in the Ordovician and Silurian:The Pr/Ph value is<1,the carbon isotope of the whole oil and n alkanes is light,and the C21TT/C23TT ratio is also<1.The dibenzothiophene content is dominant among dibenzothiophene,dibenzofuran and fluorene.These features all indicate that the oil is marine sapropelic.But their maturities are different.Oil is mature in the Silurian and highly mature in the Ordovician.(2)Oil in the Cretaceous:The Pr/Ph value is>1.6,the carbon isotope of the whole oil is relatively heavier,and the C21 TT/C23 TT ratio is>1.The oil is rich in C24 tetracyclic terpenoids and C30 rearranged hopanes.Thus,they are of continental origin.Altogether,oil in the Ordovician and Silurian strata is from the Cambrian source rocks,which are isogenous and non synchronous reservoirs.Oil in the Cretaceous strata mainly comes from continental source rocks of the northern Kuche Depression.

关 键 词：生物标志物 成熟度 白垩系 志留系 奥陶系 顺北油气田 塔里木盆地 

分 类 号：TE122.11[石油与天然气工程—油气勘探]