【摘要】 火山型被动大陆边缘是在大陆分解过程中有大量地幔物质参与,并在其中起到重要作用的一种被动大陆边缘类型,典型特征是发育向海倾斜反射体(SDR)和高纵波速度体(HVZ)。由于SDR独特的地震反射特征,很容易将其与裂谷期沉积充填,特别是与湖相烃源岩地震反射特征相混淆,通过地震火山地层学的研究有助于识别SDR。西南非海岸盆地A区块位于典型的火山型被动大陆边缘,通过区域地质分析和火山岩地震相研究,并结合类比分析综合研究后认为,研究区内裂谷期主要为火山岩充填,对烃源岩有两点不利影响:1大规模发育的火山岩侵占了烃源岩沉积的可容纳空间,不利于烃源岩发育;2裂谷期大规模发育的火山岩带来的大量高温热能对烃源岩具有烘烤作用,使其在圈闭形成之前快速生烃和异常成熟,从而失去生烃能力。因此,研究区烃源岩存在巨大风险,勘探潜力较小。更多还原

【Abstract】 Unlike sedimentary passive margins,volcanic passive margins are associated with the accretion,during continental break-up,of a thick magma crust,and characterized by seaward dipping reflectors(SDR)and high-velocity seismic zones(HVZ).The seismic resemblance of SDR sequences to lacustrine source rock is enhanced by the presence of normal faults,so these two are easily confused.Seismic volcano-stratigraphy,which is a subset of seismic stratigraphy,can be used to analyze volcanic facies imaged on seismic reflection profile,and helpful to identify SDR from lacustrine source rock.Block A is in the northern part of Southwest African Coastal Basin,which is a typical volcanic passive margin basin.On the basis of geological setting analysis,analog analysis and seismic volcano-stratigraphy analysis,we find that a rift fill of block A is mainly igneous rock,which has two adverse effects on the source rock.First,massive igneous rock takes up the accommodation space of source rock,which hampers the development.Second,massive igneous rock brings great heat,which bakes the source rock and the hydrocarbon generating ability is lost before it is trap formed.Based on these analyses,we conclude the exploration risk is very high in block A.更多还原