吐哈盆地台北凹陷天然气地球化学特征及成因分析  

Geochemical Characteristics and Origin of Natural Gas in Taibei Depression,Turpan-Harmi Basin

作　　者：赵兴齐[1] 陈践发[1] 赵红静[2] 张晨[3] 郭望[1] 周飞 刘高志[1] 

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [2]长江大学油气资源与勘探技术教育部重点实验室,长江大学地球化学系,湖北荆州434023 [3]中国石油塔里木油田公司天然气事业部,新疆库尔勒841000 [4]中国石油青海油田勘探开发研究院,甘肃敦煌736202

出　　处：《天然气地球科学》2013年第3期612-620,共9页Natural Gas Geoscience

基　　金：国家自然科学基金项目(编号:40472081);国家科技重大专项(编号:2011ZX05007)联合资助

摘　　要：根据天然气组分组成及碳、氢同位素特征,分析了吐哈盆地台北凹陷天然气的地球化学特征、成因及来源。研究区烃类气体以甲烷为主,主要分布在60%～80%之间,重烃气(C2+)含量较高,集中在20%～40%之间,天然气干燥系数(C1/C1-5)变化较大,集中在60%～80%之间,为典型的湿气;非烃气体总体含量低,主要为N2和CO2,其中雁木西地区较高含量的N2主要来源于大气氮。天然气δ13 C1值偏低,集中在-41‰～-39‰之间,δ13C2值大于-29‰,主频率为-28‰～-26‰,δ13 C3值、δ13 nC4值集中在-26‰～-24‰之间,表明台北凹陷天然气主要为煤成气。天然气δD1值分布在-239.6‰～-111.8‰之间,主频率为-240‰～-230‰,表明研究区气源母质主要形成于陆相淡水沉积环境,且天然气成熟度不高。雁木西油田部分样品天然气湿度较大且碳、氢同位素发生倒转,主要是生物降解作用所致。天然气主要处于未熟—低熟阶段(RO≤0.8%),气源对比表明,台北凹陷天然气主要来源于中侏罗统西山窑组未熟—低熟烃源岩,其次为下侏罗统八道湾组成熟烃源岩。The geochemical characteristics,origin and source of natural gas in Taibei Depression of the Tur- pan-Harmi Basin are studied based on the information of components,stable carbon and hydrogen isotopes of natural gas. The main component of hydrocarbon gas is methane ranging from 60% to 80%, and the heavy hydrocarbon gas （C2＋） which accounts for 20% to 40% possesses relatively high content. The fact that the dryness coefficient varies greatly,in the range of 60% to 80% ,shows that the gas is typically wet gas： The main component of non-hydrocarbon gas, N2 and CO2 ,has lower level of content. And N2 in Yan- muxi with higher content is mainly atmospheric nitrogen.δ13C1 varies from -41%0 to -39‰. δ13C2 is grea- ter than - 29‰, mainly in the range of - 28‰ to - 26‰. δ13 C3 and δ13 C4 mainly vary from -26‰ to -24‰. All these indicate that it is coal-derived gas. δD1 varies from -239.6‰ to -111.8‰, mainly in the range of -240‰ to -230‰, showing that gas was mainly formed in continental fresh water depositional environment and the maturity of natural gas is not high in the study area. Gas with great wetness and re- versed carbon and hydrogen isotope series are caused by biodegradation in Yanmuxi Oilfield. Thermal evo- lution of natural gas is mainly at immature to low-mature stage （Ro≤0.8%）. The gas-source correlation shows that natural gas in Taibei Depression is mainly derived from the Middle Jurassic Xishanyao Forma- tion source rocks at immature and low mature stages,while some mature stage source rocks in Badaowan Formation of Lower Jurassic also have some contributions.

关 键 词：天然气 碳、氢同位素 成因类型 成熟度 台北凹陷 吐哈盆地 

分 类 号：TE122.113[石油与天然气工程—油气勘探]