柴达木盆地原油碳同位素组成的主控因素与成因类型

Main Controlling Factors and Genetic Types of Carbon Isotopic Compositions for Crude Oils from the Qaidam Basin, China

对采集于柴达木盆地 16个油田的 4 0个原油进行了碳同位素测定 ,研究了它们碳同位素组成特征、主控因素及其成因类型。结果表明 ,柴达木盆地西部地区和北部地区原油碳同位素组成具有显著的差别 ,西部地区原油富集 1 3C,北部地区原油富集 1 2 C。研究发现 ,成油环境 (如盐度和湿度 )是决定西部盐湖相原油碳同位素组成及其变化的主要因素 ,母源性质则控制了北部淡水湖沼相原油的碳同位素组成和变化。根据原油的碳同位素组成和 Ph/ n C1 8比值特征 ,将柴达木盆地原油划分为五种成因类型。

A suite of 40 crude oil samples from 16 oil fields in the Qaidam basin were analyzed using IRMS, and features, main controlling factors and genetic types of carbon isotopic compositions for these crude oils were studied. The results show that differences in carbon isotopic compositions between the western Qaidam crude oils and the northen Qaidam crude ouils are evident. The western Qaidam crude oils are enriched in 13 C,while the northern Qaidam crude oils are enriched in 12 C. One finding is that carbon isotopic compositions of the western Qaidam curde oils from saline-hypersaline lacustrine environment are controlled mainly by oil-formed environments (e.g. salinity and humidity) and carbon isotopic compositions of the northern Qaidam crude oils from freshwater swampy-lacustrine environment rely mainly on their source natures. On the basis of their carbon isotopic compositions and Pr/Ph ratios,these oils could be divided into five genetic groups.