摘要
在系统分析柴达木盆地西部各油田 40余个原油样品碳同位素和饱和烃、芳烃组成的基础上 ,全面剖析了该地区第三系湖相原油的地球化学特征。研究结果表明 ,这些原油具有特殊的碳同位素组成和异常的生物标志物分布。其全油碳同位素偏重 ( - 2 6‰～ - 2 4‰ ) ;正构烷烃系列单体烃碳同位素分布曲线呈水平状 ,表现出类同于海相有机质的碳同位素组成特征。它们的生物标志物中正烷烃系列兼具奇碳和偶碳优势双重碳数分布模式 ;呈强植烷优势 ,Pr/Ph值大多 <0 6;伽玛蜡烷普遍异常丰富 ,C35藿烷含量高 ,表征高盐、厌氧的咸水湖相沉积环境性质。芳烃组份以萘、菲系列为主 ,而二苯并噻吩等含硫有机化合物相对含量较低 ,反映该地区咸水湖相原油源岩沉积相的特殊性。柴西各油田原油地球化学参数在区域上呈规律性变化趋势 ,与其源岩沉积相的时空变迁相一致。
Based on systematic analyses of carbon isotope, saturate and aromatic fractions of over 40 oil samples collected from the oil fields in western Qaidam Basin, the geochemical characteristics of the Tertiary saline lacustrine oils in this region was investigated. The studied results revealed the unusual carbon isotopic compositions and abnormal biomarker distributions in these oils. The oils had heavy carbon isotopic ratios (-26‰～-24‰) and flat curves of individual n-alkane isotope profile, showing similar isotopic characteristics of marine organic matter. Bimodal n-alkane distributions with odd-to-even and even-to-odd carbon predominance, low Pr/Ph (mostly lower than 0 6), high concentration of gammacerane and C 35 hopane were found in these oil samples, reflecting the high salinity and anoxic condition typical of saline lacustrine depositional environment. The aromatic hydrocarbons predominated by naphthalene and phenanthrene series with relatively low amount of organic sulfur-containing compounds such as dibenzothiophenes could be associated with the unusual saline depositional setting for the oil source rock. It was noted that the geochemical parameters of oils in various oil fields exhibited a regular spatial changes, which were consistent with the depositional phase variations of the source rocks.
出处
《地质科学》
CAS
CSCD
北大核心
2004年第4期475-485,共11页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
中国石油天然气集团公司 95重点科技攻关项目 (编号 :970 2 0 7)资助
