渤海湾盆地惠民凹陷临南洼陷沙河街组原油地球化学特征及油源对比

惠民凹陷是渤海湾盆地济阳坳陷中的一个富油气单元。系统研究惠民凹陷临南洼陷20个原油样品和4个烃源岩样品地球化学特征，分析其成熟度、沉积环境和有机质来源，利用烃源岩和原油生物标志化合物参数建立油-岩关系，筛选有效参数运用交会图和聚类统计划分原油类型和进行油源对比。研究区原油已进入成熟阶段，生油母质的沉积环境为弱氧化-弱还原的湖沼相-淡水湖相，具有陆相湖盆混合型母质特征。总体上，研究区原油有较高的饱和烃含量和较低的胶质及沥青质含量，正构烷烃为"平台式"双峰形态分布，伽马蜡烷含量较低，4-甲基甾烷含量较高。研究区内不同地区原油的地球化学特征存在一定差别，可按地区分为南带和北带。相比南带的原油，北带原油样品中4-甲基甾烷/C₂₉R、Ts/Tm比值较低，而C₂₉降藿烷/C₂₉降新藿烷、1，2，7-/1，2，6-三甲基萘、菲/∑甲基菲较高。研究区沙四段烃源岩有机质类型为Ⅲ型，有机质丰度较低；沙三段烃源岩有机质以Ⅱ型为主，有机质丰度较高，其中，沙三下亚段和中亚段是临南洼陷的主力烃源岩。通过系统对比研究区原油和烃源岩的地球化学特征，认为临南洼陷沙三、沙四段原油来自沙三下、中亚段烃源岩。 

Geochemical characteristics of crude oil and oil-source correlation of Shahejie Formation in Linnan Sub-Sag,Huimin Sag,Bohai Bay Basin

The Huimin Sag is a significant petroleum unit in the Jiyang Depression. This work reports a systematic study of the geochemical characteristics of 20 crude oil samples and 4 source rock samples collected from the Linnan Sub-Sag of the Huimin Sag and interpretations of maturity, sedimentary environment and organic matter sources. Oil-source rock relationship was established by using the biomarker parameters of the source rock and crude oil samples. To classify the oils and to interpret the oil-source correlation, various effective parameters were selected and processed using cross-plots and cluster analysis. The results showed that the crude oils have entered the mature stage, with continental-lacustrine-basin hybrid parent materials and a weakly oxidizing to weakly reducing depositional environment. Most of the crude oils had a high content of saturated hydrocarbon, low contents of resins and asphaltene, "platform" bimodal chromatograms of n-alkanes, low content of gammacerane and high content of 4-methyl steranes. According to the differences of the geochemical characteristics of certain areas, crude oils were divided into the south zone oils and the north zone oils. Compared with the south zone oils, the north zone oils possessed lower ratios of 4-methyldecane/C₂₉R and Ts/Tm, and higher ratios of C₂₉ norhopane/C₂₉ Ts, 1,2,7-/1,2,6-trimethylnaphthalene and phenanthrene/∑methyl phenanthrenes. The organic matter type of the source rocks of the fourth member of Shahejie Formation in the Linnan Sub-Sag is type Ⅲ, and the abundance of organic matter is low. The organic matter of the source rocks of the third member of Shahejie Formation is dominated by type Ⅱ, and the abundance of organic matter is high. The lower and middle sections of the third member of Shahejie Formation are the main source rocks of the sub-sag. By systematically comparing the geochemical characteristics of the crude oils and the source rocks, it was found that the crude oils from the third and fourth members of Shahejie Formation of the Linnan Sub-Sag came from the source rocks of the lower and middle sections of the third member of Shahejie Formation.