西非纳米贝盆地构造-沉积演化与油气勘探潜力

    TECTONO-SEDIMENTARY EVOLUTION AND PETROLEUM POTENTIAL OF NAMIBE BASIN AT THE PASSIVE CONTINENTAL MARGIN OF WEST AFRICA

    • 摘要: 西非纳米贝(Namibe)盆地是世界上极少数没有油气勘探的地区,以收集到的西非纳米贝盆地区域基础地质和相邻含油气盆地资料为依据,运用石油地质综合分析方法研究分析认为,纳米贝盆地构造-沉积演化经历了前裂谷阶段(P—J2)、裂谷阶段(J3—K1巴雷姆期)、过渡阶段(K1阿普特期)和被动陆缘期(K1阿普特晚期—现今)4大阶段;盆地发育3套潜在烃源岩,其中早白垩世巴雷姆期湖相页岩最重要;发育裂谷晚期、漂移早期和漂移晚期3套储集层;过渡单元层序早白垩世阿普特期厚层页岩为区域性盖层,晚白垩世—新生代漂移层序存在多套局部盖层;发育构造-地层圈闭与地层圈闭,断层与不整合面为主要油气运移疏导体系,存在下白垩统成藏组合和上白垩统—渐新统与中新统成藏组合2类潜在成藏组合,揭示出油气勘探前景广阔。

       

      Abstract: The Namibe Basin lies on the passive continental margin of West Africa, which is a specific large basin in the world without oil and gas exploration activities so far. Based on collected materials on basic regional geology and hydrocarbon geology from adjacent basins, using integrated petroleum geological approaches, the potentials of oil and gas in the basin are studied in this paper. The study shows that the Namibe basin has experienced four tectono-sedimentary evolution stages: pre-rift stage (P-J2), rift stage (J3-K1 Barremian), transitional stage (K1 Aptian) and passive continental margin stage (K1 late Aptian- nowadays). There are 3 sets of source rocks, predominated by the early Cretaceous Barem lacustrine shale; There occur 3 sets of reservoirs in late rift, early drift and late drift stages respectively. The thick transitional sequence of Lower Cretaceous Aptian shale is an effective regional cap rock, in addition to several local caprocks in the Late Cretaceous-Cenozoic drift sequence. Structural and stratigraphic traps dominate the basin. Faults and unconformity boundaries are the main paths for migration. There occur two possible source-reservoir-cap assemblages in the Lower Cretaceous and Upper Cretaceous-Oligocene-Miocene respectively, with great oil and gas exploration prospect.

       

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