东非马任加盆地油气地质特征与区带评价

    Hydrocarbon in the Majunga Basin in East Africa: geological characteristics and zonation evaluation

    • 摘要: 东非大陆边缘近年来持续的大气田发现引起国内外油公司广泛的关注,马任加盆地作为东非地区勘探程度极低的盆地之一,相关油气勘探成果报道较少。基于国际商业油气田数据库IHS和Tellus,梳理了盆地油气勘探历程、区域构造沉积演化和成藏要素特征。结果表明:马任加盆地是叠加在晚古生代—侏罗纪裂谷之上的中—新生代被动陆缘盆地,经历了同裂谷、马达加斯加陆块裂开和被动大陆边缘3个演化阶段,形成了东部陆相,往西过渡到海相的沉积地层序列。截至目前,盆地尚无商业油气发现,潜在的成藏组合包括白垩系构造-地层成藏组合和三叠系—侏罗系Sakamena/Isalo组构造成藏组合2套。运用国内含油气区带评价方法,将盆地划分为西部深水区带等5个油气远景区带,综合评价认为,西部深水区带为最有利区带,下一步应加强地震工作量部署,落实有利圈闭位置。

       

      Abstract: In recent years, the continuous discovery of large gas fields along the East African continental margin has attracted widespread attention from oil companies in the world. The Majunga Basin, as one of the least explored basins in the East African region, the outcomes of oil and gas exploration are few. Based on the international commercial oil and gas field databases IHS and Tellus, we reviewed the oil and gas exploration history, regional structural sedimentary evolution, and characteristics of the hydrocarbon accumulation elements of the basin. The research results indicate that the Majunga Basin is a Mesozoic-Cenozoic passive continental margin basin superimposed on the Late Paleozoic-Jurassic rift, having experienced three evolutionary stages: syn-rift, Madagascar block breakup, and passive continental margin, forming a sedimentary sequence that transitions from terrestrial in the east to marine in the west. To date, no commercial oil and gas discoveries have been made in the basin, and the potential hydrocarbon accumulation combinations include the Cretaceous structural-stratigraphic and Triassic-Jurassic Sakamena/Isalo Formation structural combinations. Using hydrocarbon-bearing zone evaluation methods commonly applied in China, five oil and gas prospective zones, including the western deepwater zone of the basin, have been delineated. The comprehensive evaluation showed that the western deepwater zone is the most favorable zone, and we recommended that the next step should strengthen the deployment of seismic work to confirm the location of favorable traps.

       

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