东北石油大学学报2025，Vol.49Issue(2)：46-59,70,15.DOI:10.3969/j.issn.2095-4107.2025.02.004
北部湾盆地涠西南凹陷深层原油和烃源岩地球化学特征及成藏模式
Geochemical characteristics and accumulation models of crude oils and source rocks in the deep strata of Weixinan Sag,Beibuwan Basin
摘要
Abstract
Oil and gas exploration in the Weixinan Sag of the Beibuwan Basin has predominantly targeted the middle and shallow layers,while deep layers remain underexplored with few oil and gas discoveries.Using analytical data on the physicochemical properties,group composition,gas chromatography(GC)of saturated hydrocarbons,and gas chromatography-mass spectrometry(GC-MS)of saturated hydrocar-bons,as well as total organic carbon,rock pyrolysis,group composition,gas chromatography(GC)of saturated hydrocarbons,and gas chromatography-mass pectrometry(GC-MS)of saturated hydrocarbons of source rocks,this study applies organic geochemical techniques to investigate the geochemical charac-teristics of deep crude oil and its source correlations and its accumulation models.The results reveal that deep crude oil in the study area is relatively light,with low kinematic viscosity at 50℃,very low sulfur content,and moderate wax content.The group composition exhibits the"two highs and three lows"characteristics:high mass fractions of saturated hydrocarbons and high saturated hydrocarbon/aromatic hydrocarbon ratios,along with low mass fractions of aromatics,non-hydrocarbons,and asphaltenes.Deep crude oil is classified into three types.Type Ⅰ crude oil shows a "bimodal" distribution of n-alkanes with significant pristane dominance,moderate tricyclic terpane content,an asymmetric "V-shaped" dis-tribution of regular steranes(ααα(20R)C27-C28-C29),and moderate 4-methyl C30 sterane content,indica-ting a genetic relationship with the middle-upper sub-member mudstones of the second member of the Liushagang Formation.Type Ⅱ crude oil exhibits a "single-peak with posterior dominance" n-alkane distribution,high tricyclic terpane content,an asymmetric "V-shaped" distribution,and high 4-methyl C30 sterane content,primarily sourced from the lower sub-member oil shales of the second member of the Liushagang Formation.Type Ⅲ crude oil is characterized by a "single-peak with anterior domi-nance" n-alkane distribution,high tricyclic terpane content,an "L-shaped" sterane distribution,and low 4-methyl C30 sterane content,mainly derived from the upper sub-member mudstones of the third mem-ber of the Liushagang Formation.Based on these findings,three deep crude oil accumulation models are proposed for the study area:"self-sourced and self-stored","adjacent-sourced and lateral-stored" and a mixed" self-sourced and self-stored with adjacent-sourced and lateral-stored" model.These results pro-vide valuable guidance for deep crude oil exploration in the Weixinan Sag of the Beibuwan Basin.关键词
深层原油/生物标志物/地球化学特征/油源对比/成藏模式/流沙港组/涠西南凹陷/北部湾盆地Key words
deep crude oil/biomarker compounds/geochemical characteristics/source correlation/accu-mulation models/Liushagang Formation/Weixinan Sag/Beibuwan Basin分类
石油、天然气工程引用本文复制引用
周刚,胡德胜,徐新德,刘爱群,钟佳..北部湾盆地涠西南凹陷深层原油和烃源岩地球化学特征及成藏模式[J].东北石油大学学报,2025,49(2):46-59,70,15.基金项目
中国海洋石油有限公司前瞻基础研究项目(KJQZ-2024-2003) （KJQZ-2024-2003）
"十四五"全国油气资源评价项目(QGYQZYPJ2022-3) （QGYQZYPJ2022-3）
