西非加蓬海岸盆地北加蓬次盆油气藏评价及勘探潜力分析

Reservoir evaluation and exploration potential analysis of North Gabon subbasin of Gabon coast basin in West Africa

加蓬海岸盆地为西非盆地群组成部分，自白垩纪以来，盆地经历了裂谷期、过渡期和被动大陆边缘沉积时期。北加蓬次盆油气成藏以盐上层系为主，油气藏分布受区域构造演化影响，油气聚集带与区域构造带走向一致。上白垩统Azile组泥岩为主要源岩，该套烃源岩在中新世达到生烃高峰。上白垩统Anguille组和Pointe Clairette组砂岩为主要储层，盆地成藏模式为下生上储型，油气以近距离侧向运移为主。盆地存在压力封存箱现象。Anguille组大套泥岩形成了异常压力系统，地层压力系数在1.3-1.66。根据盆地浊积砂体分布特征，认为北加蓬次盆西南部地区上白垩统有效烃源岩和浊积扇均发育的地区油气成藏条件优越，是未来勘探的重点地区。

Gabon coast basin is one of the West Africa group basins. Since Cretaceous, Gabon basin undergoes lift period, transi？tion period and passive continental margin period. Oil reservoirs in North Gabon sub-basin mainly locate in post salt layers, which are controlled by regional tectonic framework, and regional structural belt is identical with oil and gas concentration zone. Azile mudstone of Upper Cretaceous which reaches generate-oil and gas peak in Miocene Period of Tertiary is the main source rock in this area. Anguille of Upper Cretaceous and member Clairette of Pointe sandstone are the main reservoirs in this district, of which the type of oil and gas reservoirs is upper source rocks and lower reservoir rocks, and the oil and gas migration is in a short dis？tance. There is pressure close box in oil reservoir. Because Anguille sandstone is limited by surrounding mudstones, abnormal pres？sure system appears in Anguille oil reservoirs whose pressure coefficient reaches 1.3-1.66. According to Anguille sandstone distri？bution, the developed effective source rocks and turbidite fan areas in this district with the favorable accumulation conditions are the key areas of future exploration.