金湖凹陷原油轻烃的地球化学特征及意义

对金湖凹陷40个原油样品进行轻烃组分、Mango参数和成熟度等研究。甲基环己烷指数指示出该凹陷原油的干酪根类型为Ⅰ-Ⅱ型；C₅轻烃特征显示有机质来源既有腐泥型也有腐殖型；Mango轻烃参数K₁值基本符合轻烃稳态催化动力学轻烃成因模式，暗示着该凹陷原油有着相似的沉积环境；C₅-C₇轻烃三环优势大于五环和六环优势，表明该地区原油主要来源于湖相沉积环境的烃源岩；原油轻烃组分中的庚烷值和异庚烷指数都较低，原油成熟度低，原油形成温度在120~128℃之间。为进一步认识金湖凹陷原油和烃源岩的地球化学特征提供科学依据。

Geochemical Characteristics of Light Hydrocarbons in Jinhu Sag and It′s Significance

In this paper,we measure the chemical composition of light hydrocarbons,the Mango parameters,and thermal maturity for 40 oil samples from the Jinhu sag.The methylclohexane index reveals that the oils are derived from type I and type II kerogen.The C₅ light hydrocarbons indicate that the organic matter is composed of both sapropelic and humic.The Mango parameters K₁ is consistent with the chemically stable structure model of light hydrocarbons,suggesting that the oils would be formed in the similar depositional environment of organic matter.Predominance of C₅ to C₇ tricyclic light hydrocarbon abundance is more than that of pentacyclic and hexacyclic light hydrocarbon,showing that oils are mainly originated from lacustrine source rocks.Both heptane value and isoheptane index are little,indicating the thermal maturity of oils is low.The formation temperature of oils is in range of 120-128℃.The results provide the geochemical information for further understanding of oils and source rock in the Jinhu sag. 