关键词: 有机地球化学, 轻烃, 塔里木盆地

Abstract: According to the steady-state catalytic hypothesis by Mango's about the origin of light hydrocarbons in crude oil and the relative plot between the percentage of the "parent" compounds (methylhexanes) in C7 and the abundance ratio of two kinds of the "daughter" compounds (1,1-and 1,3-dimethylcy-clopentanes; dimethylpentanes+3-ethypetane).The 141 kinds of crude oils from various tectonic units and layers of Tarim Basin are classified into two types (type A and B) and four sub-types.In order to testify the effectiveness of the classification and understand the factors which influence the classification of crude oils, trace elements, gas chromatograms of C₁₄⁺ compounds in saturate fractions, the compositions and distributions of biomarkers in various crude oils have been studied comprehensively.Because there are obvious differences in geochemical features and some distribution regularities in various crude oils, the new classification of crude oils are effective in Tarim Basin, especially to oil and gas regions with high maturity. The main factors which influence the classification of crude oils on light hydrocarbons may be the catalyst compositions controlled by depositional environments.In addition, the type of kerogen may have some influence on this classification, these results support Mango's viewpoints.

Key words: organic geochemistry, light hydrocarbon, Tarim Basin, crude oil, classification