柴达木盆地原油烃类地球化学特征

柴达木盆地是我国重要的中新生代含油气盆地。已发现的18个油田分布于柴北地区和柴西地区,且以柴西地区最多。两个地区原油的成因截然不同,引起了国内外学者的关注。对采集于两地区13个油田的16个原油样品中烃类生物标志化合物进行了系统的分析,研究了它们的地球化学特征。生物标志化合物的分布和组成特征指示了西部原油形成于强还原咸水—超咸水湖相,北部原油形成于弱氧化淡水湖沼相;西部原油的母质主要为菌藻类,北部原油更多的来自陆源高等植物。根据生物标志化合物特征,并结合碳同位素组成,将柴达木盆地原油划分为两大类7种次级成因类型。 

GEOCHEMICAL CHARACTERISTICS OF HYDROCARBONS IN CRUDE OILS FROM THE QAIDAM BASIN

The Qaidam Basin is an important Mesozoic-Cenozoic petroliferous basin in west China. 18 oil fields have been found in the western and northern Qaidam Basin since oil was first discovered in the late 1950s, and the western Qaidam Basin contains more oil fields compared to the northern Qaidam Basin. Geneses of crude oil in these 2 areas are significantly different. Hydrocarbon biomarkers in 16 crude oil samples from 13 oil fields of the 2 areas are analyzed and their geochemical characteristics are studied. The distribution and composition of biomarkers indicate that, crude oils in the western area originated from source-rocks under weak oxidation and freshwater-marsh lacustrine environment. Crude oils in the western area derived mainly from bacteria and algae; however, those in the northern area from terrestrine high plants. According to the characteristics of biomarkers and the compositions of carbon isotope, crude oils in the Qaidam Basin can be divided into 2 genetic groups and 7 genetic subgroups.