摘要
四川盆地二叠系茅口组油气资源丰富,元坝地区茅口组油气勘探虽有发现,但油气成藏期次与成藏过程认识存在分歧,勘探潜力认识不明。为此,本次研究从流体包裹体入手,采用薄片观察,包裹体均一温度与盐度测定、激光拉曼等分析手段,并结合埋藏-热演化史,对元坝地区茅口组油气成藏过程进行深入研究。结果表明:元坝地区茅口组流体包裹体的宿主矿物主要为孔洞方解石胶结物,捕获两期流体包裹体。第一期包裹体以气液两相盐水包裹体和气液两相含烃包裹体为主,气相成分主要为CH4,宿主矿物为第2期方解石,盐水包裹体均一温度集中在85~115℃,盐度w(NaCl)为0.53%~19.99%。第二期流体包裹体赋存在第三期方解石宿主矿物中,发育气液两相盐水包裹体、气液两相含烃包裹体、气烃包裹体以及少量沥青包裹体,同期盐水包裹体均一温度主要集中在115~160℃,盐度w(NaCl)为0.88%~20.07%。包裹体均一温度指示元坝地区茅口组油气连续充注,两期盐水包裹体盐度整体呈正态分布,表现为低盐度特征,流体包裹体温度-盐度无明显相关性,显示该地区地层封闭性可能遭到过破坏。结合地层埋藏史分析,由于该区溶蚀孔洞充填较早,缺乏显著的原生油藏形成阶段,天然气充注时间主要在早侏罗世之后。该区目前发现的气藏主要为干酪根裂解生气,伴随着少量的原油裂解气,因构造调整捕获而成,天然气聚集成藏潜力有限。
The Permian Maokou formation in the Sichuan basin contains abundant oil and gas resources.A_(l)though hydrocarbon discoveries have been made in the Maokou formation within the Yuanba area of the northern Sichuan basin,discrepancies exist regarding the timing and process of hydrocarbon accumulation,resulting in an unclear assessment of the exploration potential.This study investigates the hydrocarbon accumulation process in the Maokou formation of the Yuanba area through comprehensive analysis of fluid inclusions,including thin section observation,homogenization temperature and salinity measurements,laser Raman spectroscopy,and burial-thermal evolution history analysis,to clarify the accumulation timing and mechanism.The results demonstrate that fluid inclusions in the Maokou formation of the Yuanba area primarily occur in pore-filling calcite cement,recording two distinct periods of fluid entrapment.The first period,hosted in second-stage calcite,comprises gas-liquid two-phase brine inclusions and gas-liquid two-phase hydrocarbon inclusions,with methane(CH4)as the dominant gaseous component.These brine inclusions exhibit homogenization temperatures ranging from 85 to 115°C and salinities between 0.53%and 19.99%NaCl eqv.The second period,occurring in third-stage calcite,contains gas-liquid two-phase brine inclusions,gas-liquid two-phase hydrocarbon inclusions,gas hydrocarbon inclusions,and minor asphalt inclusions.These brine inclusions show homogenization temperatures primarily between 115 and 160°C,with salinities ranging from 0.88%to 20.07%NaCl eqv.The homogenization temperature data indicate continuous hydrocarbon charging in the Maokou formation of the Yuanba area.Both periods of brine inclusions display normally distributed salinity values with generally low salinity characteristics.The absence of a significant correlation between inclusion temperatures and salinities suggests potential disturbance of the formation sealing system.Burial history analysis reveals that dissolution pores were filled early,without a distinct primary reservoir formation stage.Natural gas charging predominantly occurred after the early Jurassic.The currently discovered gas reservoirs in the area mainly originated from kerogen cracking,with minor contributions from crude oil cracking gas.These reservoirs were formed through tectonic adjustment and capture processes,exhibiting limited potential for natural gas accumulation and storage.
作者
邓剑
宁科科
李让彬
蒋杰
邹玉涛
袁龙
田亚铭
DENG Jian;NING Keke;LI Rangbin;JIANG Jie;ZOU Yutao;YUAN Long;TIAN Yaming(SINOPEC Exploration Company,Chengdu,Sichuan 610041,China;College of Energy(College of Modern Shale Gas Industry),Chengdu University of Technology,Chengdu,Sichuan 610059,China;College of Earth and Planetary Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China)
出处
《矿物岩石》
北大核心
2025年第2期151-159,共9页
Mineralogy and Petrology
基金
国家重点研发计划(编号:2023YFC2906503-02)
中国石化科技部项目(编号:P24235)。
关键词
茅口组
流体包裹体
激光拉曼
均一温度
油气成藏
四川盆地
Maokou formation
fluid inclusions
laser Raman
homogenization temperature
hydrocarbon accumulation
Sichuan basin
