西湖凹陷古近系平湖组“断−脊−砂”耦合成藏差异性  

Fault tectonic ridge sand body hydrocarbon accumulation in the Pinghu Formation of Paleogene in Xihu Sag

作　　者：张喜淳 徐昉昊[1] 徐国盛[1] 刘金水 刘建斌 张武 黎建 梁浩然 ZHANG Xichun;XU Fanghao;XU Guosheng;LIU Jinshui;LIU Jianbin;ZHANG Wu;LI Jian;LIANG Haoran(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;CNOOC China Limited,Shanghai Branch,Shanghai 200335,China)

机构地区：[1]油气藏地质及开发工程全国重点实验室(成都理工大学),成都610059 [2]中海石油(中国)有限公司上海分公司,上海200335

出　　处：《成都理工大学学报(自然科学版)》2025年第2期344-361,共18页Journal of Chengdu University of Technology: Science & Technology Edition

基　　金：国家自然科学青年基金项目(42302186);成都理工大学研究生教改项目(2023YJG212)。

摘　　要：为了研究平湖组断层、构造脊、砂体对油气运聚的控制作用,深化油气成藏规律认识,以西湖凹陷平湖构造带近年来油气勘探取得突破的Z构造为例,基于三维地震、钻井、天然气地球化学、流体包裹体等资料,分析平湖组断裂体系特征,探讨影响油气运聚的差异性因素。实验结果表明,平湖组天然气主要为有机成因煤型气,δ^(13)C_(1)介于−43.1‰~−33.9‰,δ^(13)C_(2)介于−29.5‰~−25.3‰;通过碳同位素拟合计算得到的Ro呈现“浅层高、深层低”的特征;流体包裹体荧光特征表现为2期成藏,均一温度频率图表现为“双峰”,分别集中在145~150℃和155~160℃。综合分析认为:①Z构造发育大量NE向继承性断裂,现今油气藏围绕控圈断裂近洼带一侧分布;将平湖组纵向划分为下、上2套成藏组合,双源供烃背景下油气2期充注,天然气为近源垂向和远源侧向混合运移的混源气。②下成藏组合为“不整合面−反向断层−断槽砂”输导体系,油气主垂向辅侧向双向充注;上成藏组合为“反向断层−断坡砂”输导体系,天然气主远源侧向充注。③Z构造油气成藏过程较复杂,根据优势运移通道断层和构造脊与砂体之间的耦合配置关系,建立下成藏组合“断−脊−砂联控原生−次生立体成藏模式”和上成藏组合“断−脊−砂联控次生环凸成藏模式”,天然气具备沿断层走向“顺断扶墙走”的高效运移特征。The aim of this work is to study the controlling effect of faults,tectonic ridges,and sand bodies on hydrocarbon migration and accumulation in the Pinghu Formation,and deepen our understanding of the hydrocarbon accumulation law therein.Taking the Z structure,which has been identified in oil and gas exploration in Xihu Sag in recent years,as an example,and based on 3D seismic,drilling,natural gas geochemistry,and fluid inclusion data,the fault system characteristics of the Pinghu Formation are analyzed and the factors affecting oil and gas migration and accumulation are discussed.The experimental results show that the gas in the Pinghu Formation is mainly coaliferous,with δ^(13)C_(1) ranging from−43.1/‰ to−33.9/‰ and δ^(13)C_(2) ranging from−29.5‰to−25.3‰.The behavior inferred from the reflectance,Ro,of vitrinite can be described as“high in shallow layers and low in deep layers.”The fluorescence characteristics of fluid inclusions show two phases of accumulation,and the homogenization temperature shows two peaks concentrated at 145~150℃and 155~160℃.Our comprehensive analysis shows that:(1)A large number of NE trending faults have developed in the Z structure,and hydrocarbon reservoirs are distributed around the control zone fault near the present depression zone.The Pinghu Formation is vertically divided into two sets of accumulation assemblages,and the oil and gas have two stages of charging under the background of a dual-source hydrocarbon supply.The natural gas is coaliferous,produced by near-source vertical and far-source lateral mixed migration.(2)The lower reservoir formation is an antithetic fault–fault channel sand transport system,with oil and gas being mainly vertically supplemented by lateral bidirectional injection.The upper reservoir formation is an antithetic fault–fault slope sand transport system,and natural gas is mainly sourced laterally.(3)The process of oil and gas accumulation in the Z structure is relatively complex.Based on the complex relationships between the

关 键 词：西湖凹陷 古近系平湖组 断裂体系特征 "断−脊−砂"耦合 成藏差异性 

分 类 号：P618.13[天文地球—矿床学]