高邮凹陷原油轻烃地球化学特征及群组划分

 高邮凹陷是苏北盆地油气潜力最大的凹陷，对该凹陷马家嘴、黄珏、富民、永安等9大油田原油样品的C₆~C₇轻烃特征、Mango轻烃参数及轻烃对比、蚀变星图和成熟度参数展开系统对比研究。C₆~C₇轻烃中富含正己烷，苯相对含量低，正庚烷、甲基环己烷和二甲基环戊烷的相对含量相差不大，显示高邮凹陷原油母质类型为腐泥-腐殖型。Mango轻烃参数K₁平均值为0.97，表明高邮凹陷原油具有相似的沉积环境；上含油气系统的K₂较大，平均值为0.31，表明陆源输入较大；中含油气系统的K₂较小，平均值为0.22，表明水源输入较大，下含油气系统介于两者之间，K₂平均值为0.27。由轻烃星图对比、庚烷值和异庚烷指数显示，上含油气系统的成熟度高，保存条件好；中含油气系统原油成熟度低，受次生演化作用明显；下含油气系统原油处于成熟阶段。

Geochemical Characteristics and the Group Division of Light Hydrocarbons in Crude Oil from Gaoyou Sag

Gaoyou sag has the greatest potential in oil and gas reserves in Subei Basin. This paper investigates the characteristics of C₆, C₇ light hydrocarbons from nine oilfields in Gaoyou sag, their Mango parameters, the transformation star diagram and maturity degree of crude oils, and makes comparisons among them. C₆ light hydrocarbon is rich in n-hexane, and relatively poor in benzene. Among the components of C₇ light hydrocarbon, the contents of n-heptane, methyl cyclohexane and dimethyl cyclopentane have little difference, indicating the organic matter sources are both sapropelic type and humic type. The average Mango parameter K₁ of the light hydrocarbons is 0.97, suggesting that the oils have similar sedimentary environments. The K₂ of the up petroleum system is large, averaging 0.31, indicative of large terrestrial input. The K₂ of the middle petroleum system is smaller, averaging 0.22, indicative of large water input. Comparison of the light hydrocarbons, their transformation star diagrams, heptane value, and isoheptane index indicate the up petroleum system is in high maturity and has good preservation conditions, while the middle petroleum system is in low maturity, and the down petroleum system is under the mature stage. The analysis of the crude oils in Gaoyou sag and their group division may provide help for oil and gas exploration in this area.