对准噶尔盆地东部彩南油田侏罗系油藏原油族(组)群类型的认识

RECOGNITION OF CRUDE OIL TYPES IN THE JURASSIC RESERVOIRS OF CAINAN OILFIELD, THE EAST JUNGGAR BASIN

彩南油田周围及外缘各凹陷内,不同程度地发育了石炭系、二叠系、三叠系以及侏罗系等生油层系,均发育有暗色泥岩。长期以来对彩南油田侏罗系油藏原油的来源没有定论。根据原油稳定碳同位素和生物标志化合物地球化学特征可以将研究区原油划分为5个族群,以彩南油田侏罗系油藏为主的第Ⅳ族群原油δ13C值分布在-27.9‰～-29.0‰之间,Pr/Ph值多数在2.5以上,生物标志物特征非常一致,该类原油在准东地区分布广泛,应该来源于中、下侏罗统煤系地层的湖相烃源岩,有机质类型为腐泥-腐殖混合型,而并非不同时代、不同有机相烃源岩生烃的混合产物。

Many oilfields including Cainan with reservoirs aged from the Carboniferous to the Jurassic have been found in the East Junggar Basin. Dark mudstones exist in different sags around Cainan oilfield ,and there hasn,t been a conclusion about the oil origin of the Jurassic reservoirs in the area.According to the geochemical characters of stable carbon isotope and biomarkers,oils can be distinguished into five types. Oil of the Jurassic reservoirs in Cainan is conformity,and is characterized the δ13C value of -27.9‰ to -29.0‰ and the Pr/Ph ratio above 2.5, possibly is originated from mixed organic matters of sapropel and humus in lacustine source rocks of the Middle and the Lower Jurassic coalbearing sequence,instead of the mixture of hydrocarbons from different epochs and different facies of source rocks.