北部湾盆地涠西南凹陷原油成因类型及分布特征

在大量采集涠西南凹陷烃源岩和原油饱和烃色谱、色谱-质谱、碳同位素等资料基础上，对涠西南凹陷烃源岩特征进行分析，根据地球化学特征差异划分为A、B、C等3类烃源岩。系统分析原油有机地球化学特征差异性，对不同层系原油物性进行统计梳理，依据甾、萜烷、饱和烃组成等进行原油成因类型划分，将涠西南凹陷原油分为A、B1、B2、C1和C2等3大类5亚类。通过油源精细对比和原油空间分布特征分析，A类原油来源于A类源岩，主要分布在1号、2号和3号断裂附近及东南部的斜坡部位；B1和B2类原油来源于B类源岩，其中B1类原油主要分布在2号断裂附近，B2类原油主要在3号断裂附近；C1和C2类原油来源于C类源岩，C1类原油分布在与B1类原油相近的区域，C2类原油主要集中分布在2号断裂与3号断裂接近交互的部位。

Genetic Types and Distribution of Crude Oil in Weixi'nan Depression,Beibuwan Basin

In this work, the characteristics of the source rocks in the Weixi'nan Sag are analyzed, based on a large amount of data from saturated hydrocarbon chromatography, mass spectrometry chromatography, and carbon isotope ratios, which were obtained from rock and crude oil samples. According to their geochemical characteristics, the source rocks are classified into three types (A, B, and C). Differences in the organic geochemical characteristics of the crude oils in the Weixi'nan Sag are also analyzed systematically, and their physical properties are analyzed statistically. Based on the genetic types according to the strontium, decane, and saturated hydrocarbon compositions, the crude oils are classified into five subgroups (A, B1, B2, C1, and C2). A detailed comparison of oil sources, and the analysis of the spatial distribution of the crude oil, show that type-A crude oil originates from type-A source rock, and is mainly distributed near fractures No. 1, 2, and 3, on the slopes in the southeast of the Weixi'nan Sag. Type-B1 and type-B2 crude oils originate from type-B source rock; type-B1 crude oil is mainly distributed near fracture No. 2, and type B2 crude oil is mainly concentrated near fracture No. 3. Type-C1 and type-C2 crude oils come from type-C source rock; type C1 crude oil is distributed in areas close to those of type-B2 crude oil, while type-C2 crude oil is mainly concentrated at the intersection between fracture No. 2 and fracture No. 3.