塞阿拉-普蒂瓜尔盆地油气地质特征及勘探潜力评价

Hydrocarbon geological characteristics and exploration potential evaluation of Ceara-Putiguar Basin

为了揭示塞阿拉-普蒂瓜尔盆地油气勘探潜力,以现代油气地质理论为指导,依据最新的勘探进展以及地震、钻井等资料,研究盆地的断裂系统、结构构造以及油气地质条件和成藏模式。结果表明:“两期两类”不同性质的4组断裂控制裂陷盆地的构造格局。普蒂瓜尔裂陷盆地陆上受裂陷Ⅰ期伸展断裂控制表现出南断北超的半地堑系统,海域部分主要受裂陷Ⅱ期伸展断裂系统控制表现出“南北分带”构造格局;塞阿拉裂陷盆地受裂陷Ⅱ期伸展、走滑断层控制,具有“东西分异”的特征,盆地东部表现为NW-SE走向的拉张断陷结构,而西部具有近EW走向的走滑拉分结构。塞阿拉-普蒂瓜尔盆地发育3套有效烃源岩,4类储盖组合。在盆地海域,过渡期顶部的海相泥岩是主力烃源岩,油气主要沿着断裂、不整合面等在过渡期三角洲砂岩和漂移期浊积砂岩圈闭中聚集,具有自生自储和下生上储两种成藏模式。综合油气成藏主控因素和成藏模式,指出普蒂瓜尔盆地中部坳陷带中部是有利的油气勘探区带。该研究成果对指导塞阿拉-普蒂瓜尔盆地下步油气勘探具有重要参考价值。

In order to reveal the hydrocarbon exploration potential of Ceara-Putiguar Basin,under the guidance of modern oil and gas geological theory,the fault system,structure,oil and gas geological conditions and reservoir forming model of the basin were studied according to the latest exploration progress as well as seismic and drilling dataThe results show that four groups of faults with different properties of“Two stages and two types”control the structural pattern of rift basin;The onshore Putiguar rift basin is controlled by the rift stage Ⅰ extension fault system,showing a half graben system of faulting in the South and exceeding in the north,while the offshore is mainly controlled by the rift stage Ⅱ extension fault system,showing a“North-South zoning”structural pattern;The Ceara rift basin is controlled by the extension and strike slip faults in the second stage of rifting,with the characteristics of“east-west differentiation”.The eastern part of the basin is characterized by NW-SE trending extensional fault depression structure,while the western part of the basin is characterized by nearly EW trending strike slip extensional structure.Three sets of effective source rocks and four types of reservoir cap assemblages are developed in Ceara-Putiguar Basin.In the sea area of the basin,the marine mudstone at the top of the transition period is the main source rock.Oil and gas are mainly accumulated in the delta sandstone trap in the transition period and turbidite sandstone trap in the drift period along the fault and unconformity surface.There are two reservoir forming modes:self generation-self storage and lower generation-upper storage.Based on the main controlling factors and reservoir forming model of oil and gas accumulation,it is pointed out that the middle of central depression in Putiguar Basin is a favorable oil and gas exploration area.The research results have important reference value for guiding next oil and gas exploration in Ceara-Putiguar Basin.