伊拉克中部油区油气成藏要素特征及成藏模式

Characteristics of Oil and Gas Accumulation Elements and Model,Central Iraq

美索不达米亚盆地是全球油气最富集的盆地之一,研究区位于该前陆盆地的斜坡带,其地质认识程度低,对油气成藏的研究不系统。基于地震剖面和烃源岩热解数据,较为系统地研究了伊拉克中部油区油气成藏要素。研究表明,该区正断层未断穿新生代地层,断裂活动中部最强,北部较弱,南部最弱;褶皱活动中部最强,南部稍弱,北部最弱。早白垩世-中白垩世期间,研究区处于弱伸展构造环境;晚白垩世Hartha组沉积时期,断层发生正反转,研究区处于弱挤压构造环境;晚白垩世末到始新世,研究区处于弱伸展构造环境;渐新世,褶皱作用开始;中新世,构造格局基本定型。上白垩统Khasib组-Hartha组砂屑灰岩和下白垩统Zubair组砂岩是研究区主要储层。主力烃源岩为中侏罗统Sargelu组和上侏罗统-下白垩统Chiagara组,次要烃源岩为下白垩统Ratawi组和Zubair组。综合分析认为:与油源断裂紧临的背斜圈闭是研究区最有利的油气聚集场所。侏罗系顶部发育良好的盖层,可为下伏主力烃源岩排出烃类的成藏提供良好的封盖条件,推测中-下侏罗统具有较大的油气勘探潜力。

The Mesopotamian Basin is one of the most petroliferous basins in the world,and the study area is located in the slope zone of its foreland basin.The geological knowledge of the study area is low,and the study of hydrocarbon accumulation is not systematic.Based on the seismic profile and source rock pyrolysis data,the hydrocarbon accumulation factors of central Iraq are systematically studied.The study shows that the faults in this area have not cut through the Cenozoic,and the fault activity is the strongest in the central part,weaker in the north and weakest in the south,while the fold activity is the strongest in the central part,slightly weaker in the south and weakest in the north.During the Early-Middle Cretaceous,the study area was in a weak extensional tectonic setting.During the deposition of the Hartha Formation in the Late Cretaceous,the fault occurred positively and inversion happened,when the study area was in a weak compressional setting.From the end of the Cretaceous to the Eocene,the study area was in a weak extensional tectonic setting.Oligocene,the beginning of the fold;the Miocene,the structural pattern is basically stereotyped.Khasib-Hartha limestone and Zubair sandstone are the main reservoirs in the study area.The main source rocks are the Middle Jurassic Sargelu Formation and the Upper Jurassic-Lower White Chiagara Formation.The secondary source rocks are the Lower Cretaceous Ratawi Formation and the Zubair Formation.According to the comprehensive analysis,the anticline trap close to the migration pathway(fault)is the most favorable for oil and gas accumulation.The well-developed caprocks at the top of the Jurassic provides good sealing conditions for the hydrocarbons discharged from the main source rocks.It is speculated that the Middle-Lower Jurassic has great oil and gas exploration potential.