柴北缘冷湖构造带与马北油田原油地球化学特征对比

摘要

The distributions and compositions of biomarkers of 26 samples of crude oils from Lenghu structure zone and Mabei oilfield in the northern Qaidam Basin were analyzed.The results show that the crude oil from Mabei oilfield is characterized by relatively lower Pr/Ph (＜2.0) and higher gammacerane index (0.10-0.20),and rich in C27 steranes relative to C29 steranes together with elevated diasteranes,suggesting that the oil should be derived from Middle Jurassic lacustrine mudstones in adjacent hydrocarbon-generating sag;however,for the crude oil from Lenghu structure zone,the Pr/Ph (2.0-2.5) is relatively higher,and gammacerane index (＜0.05) is lower,and C29 steranes surpass C27 homologues.These characteristics might reveal that they are generated by lower Jurassic lacustrine mudstones.%通过对冷湖构造带和马北油田26个原油样品中生物标志物分布与组成特征的系统分析,发现马北油田原油中姥植比(低于2.0)相对偏低,伽马蜡烷指数(0.10～0.20)相对偏高,甾烷组成中明显富含指示藻类贡献的C27甾烷,且重排甾烷含量中等,它们与附近凹陷发育的中侏罗统湖相泥岩中的生物标志物分布与组成特征基本一致,显示它们之间存在成因联系;而冷湖构造带原油中姥植比(2.0～2.5)相对偏高,伽马蜡烷指数(低于0.05)相对偏低,明显富含指示陆源有机质贡献的C29甾烷,且重排甾烷含量相对丰富,这一系列特征均明显有别于马北油田原油,而与冷湖地区发育的下侏罗统湖相泥岩中的生物标志物分布与组成特征相吻合,表明该地区发育的下侏罗统湖相泥岩是其主力烃源岩.