油气沿断层垂向运移特征及主控因素分析——以东海盆地西湖凹陷平湖斜坡为例  

Characteristics and main controlling factors for vertical hydrocarbon migration along faults:a case study of Pinghu slope in Xihu Sag,East China Sea Basin

作　　者：郭刚 苏圣民 Guo Gang;Su Shengmin(CNOOC Research Institute Co.,Ltd.)

机构地区：[1]中海油研究总院有限责任公司,北京市100028

出　　处：《中国石油勘探》2024年第3期118-130,共13页China Petroleum Exploration

基　　金：中海油重大科技项目“中国近海新区新领域勘探技术”(KJGG2021-0300)。

摘　　要：东海盆地西湖凹陷平湖斜坡油气纵向富集差异受断层控制作用明显,但断层活动期与成藏期匹配关系差,油气成藏时断层处于不活跃期(简称静止断层),明确油气沿静止断层垂向运移特征及影响因素,可以为西湖凹陷或相似地区油气勘探提供理论依据。为此,综合测井、录井、地震等资料和包裹体均一温度及盐度、岩石热解等分析测试数据,研究平湖斜坡油气供烃层系与成藏期次,确定油气沿静止断层垂向运移特征及影响因素。结果表明,平湖斜坡供烃层系为宝石组和平湖组好—优质的成熟烃源岩,油气纵向上主要富集于平中段—平上段,具有下生上储的运聚特征。存在玉泉组—柳浪组沉积期和三潭组沉积期至今两期油气充注,断层主要活动时间为宝石组—龙井组沉积期,与成藏期匹配关系差,油气晚期沿静止断裂带发生了垂向运移。油气能够沿静止断层垂向运移的影响因素包括断裂带宽度、烃源岩层压力和断裂带排替压力。研究区断裂带宽度分布在138~288m之间,与油气垂向运移距离呈正相关关系。烃源岩层压力经历了复杂的演化过程,成藏期压力略低于现今,但已发育弱超压或超压,现今和成藏期压力系数越高,油气垂向运移距离越大。断裂带排替压力主要分布在0.2~3.5MPa之间,与油气垂向运移距离呈负相关关系。基于3个影响因素与油气垂向运移距离的相关关系,建立了断层垂向输导能力定量评价公式,评价结果与油气最大运移距离具有明显的正相关性,据此确定了平湖斜坡有利勘探层系为F2和F5断层附近的平湖组和花下段。The vertically differential hydrocarbon enrichment in Pinghu slope in Xihu Sag was significantly controlled by faults.But there is a poor correlation between the timing of fault activities and the period of hydrocarbon accumulation,that is,faults were inactive(hereinafter referred to as“static faults”)in hydrocarbon accumulation periods.As a result,a clear understanding on the characteristics and main controlling factors for vertical hydrocarbon migration along static faults enables to provide a theoretical basis for petroleum exploration in Xihu Sag or similar areas.The comprehensive wireline logging,mud logging,seismic data,and core testing data such as homogenization temperature and salinity of inclusions,and rock pyrolysis are used to analyze the hydrocarbon supply formations and periods of hydrocarbon accumulation,and determine characteristics and main controlling factors for vertical hydrocarbon migration along statistic faults.The study results show that hydrocarbon was supplied by the good-superior mature source rocks in Pinghu Formation and Baoshi Formation,and vertically enriched in the middle-upper parts of Pinghu Formation,showing characteristics of lower source rock and upper reservoir.Two stages of hydrocarbon charging occurred during the deposition periods of Yuquan-Liulang Formation and Santan Formation-present.While faults were mainly active during the deposition period of Baoshi-Longjing Formation,which had poor matching relationship with hydrocarbon accumulation period,and hydrocarbon migrated vertically along static faults in the late stage.The influencing factors for the vertical hydrocarbon migration along static faults include the width of fault zone,source rock pressure,and displacement pressure in the fault zone.In the study area,the width of fault zone ranges in 138-288 m,which has a positive correlation with the distance of vertical hydrocarbon migration.The source rock pressure experienced a complex evolution process,with a slightly lower pressure in the hydrocarbon accumulation pe

关 键 词：静止断层 油气垂向运移 断裂带结构 烃源岩层压力 断裂带排替压力 输导能力 

分 类 号：TE112.1[石油与天然气工程—油气勘探]