尼日尔三角洲石油地质特征

Petroleum Geological Characteristics of Niger Delta Basin

尼日尔三角洲盆地是非洲西部近年来油气勘探开发活动最活跃的地区之一。从沉积地层、生储盖组合、构造与圈闭以及油气藏分布等方面简要阐述了尼日尔三角洲石油地质特征。新生界自下而上划分为3个组,即阿卡塔组、阿格巴达组和贝宁组,均为穿时的地层单元,阿卡塔组为主要烃源岩层,阿格巴达组砂泥岩互层为主要的油气储盖层。滚动背斜及其伴生构造是盆地陆上和浅海区油气聚集的最主要圈闭类型,泥岩底辟及其相应的逆冲断裂构造是深海区油气聚集的最主要圈闭类型;盆地圈闭高度和油气柱高度普遍较小,以轻质原油为主,品质好;储层物性好,天然能量充足,自然产能很高。

Niger Delta Basin has been one of the active oil and gas exploration areas in Africa for recent years.The geological characteristics of Niger Delta Basin were described from the aspects of sedimentary strate,the assembly of oil genesis,reserves and cap-rocks,structures and traps and as well as hydrocarbon distribution.From the bottom to top,the Cenozoic system in the basin is divided into three formations,such as Akata,Agbada and Beining Formation.These three formations are all diachronic units.Akata Formation is the main source rock.Agabada is formed by several sand groups.The top of every sand group is the main oil and gas reservoir,the shale between the sand groups can be act as good seal rock.The gentle rollover anticline and associated structure are the main and most characteristic structure styles in onshore and shallow water in Niger Delta,and also the main trap style.The shale diaper and the related thrust fault structure are the main structural style in deep water area,and thrust-faulted anticlines are the main trap style in deep water.Although the trap height and oil-gas column height are commonly small,the reservoir physical property is good,oil belongs to light oil and nature energy is sufficient,the nature productivity in the basin is very high.