摘要
对柴达木盆地北缘牛东地区古近系和侏罗系储层所产原油饱和烃馏分中各类生物标志物的分布与组成特征的分析结果表明,它们的正构烷烃系列没有奇偶优势,C29甾烷成熟度指标介于0.40~0.54之间,显示成熟原油的特征。较高的姥植比(2.57~4.33)、"阶梯状"分布的C19-26三环萜烷系列、丰富的C24四环萜烷及异常偏低的伽马蜡烷和富含各种重排类标志物等特征与冷湖构造带上的原油十分相似,表明它们来源于研究区相邻的生烃凹陷中发育的下侏罗统淡水湖沼相烃源岩。对比发现不同原油中甾烷的碳数组成存在明显差异,那些C27R/C29R和C28R/C29R小于0.20的原油应该来源于煤系烃源岩,而两个比值大于0.40的原油则来源于湖相烃源岩,呈现煤成油和湖相油并存的格局。此外,古近系储层所产原油较下侏罗统储层所产原油明显富含各种重排类标志物,如重排补身烷、重排藿烷和重排甾烷等,可能与该原油较其他原油成熟度偏高,且经历了较长距离的运移分异作用有关。
Various biomarkers in the saturate fractions of crude oils from Niudong Area in the northern Qaidam Basin were analyzed by GCMS,the result showed that their normal alkane series had no odd-even carbon number predominance,and C29 sterane maturity indicators were between 0.40～0.54,it indicated that they were matured oils.Like crude oils from Lenghu Structures,it had the characteristics of high Pr/Ph ratios(between 2.57 and 4.33),step-like C19～C26 tricyclic terpanes(C19>C20>C21>C23>C24>C25>C26),abundant C24 tetracyclic terpane and various rearranged biomarkers,abnormally low gammacerane in those crude oils,indicated that they were derived from Lower Jurassic source rocks deposited under fresh water lacustrine-swamp environment.However,some significant differences in the relative compositions of carbon numbers for C27～C29 steranes in the studied oils could be observed.For example,the C27 R/C29 R and C28 R/C29 R ratios in some oils were less than 0.20,which showed that they were derived from coal-containing sequences,the other2 oils with their contrast ratios more than 0.40 indicated that they were generated from coal-formed oil and lacustrine source rocks.Therefore,it is noted that various rearranged biomarkers such as diadrimanes,diahopanes and rearranged steranes are relatively abundant in the crude oils from Paleogene reservoir,compared with the oils from Lower Jurassic reservoirs.It can be related to higher maturity and long migrated distance.
出处
《长江大学学报（自然科学版）》
CAS
2018年第7期14-21,90,共9页
Journal of Yangtze University(Natural Science Edition)
基金
国家自然科学基金项目(41272169)
国家科技重大专项(2008ZX05025-003-001)
