非洲加蓬×区块油气成藏条件及勘探潜力分析

Analysis of Hydrocarbon Accumulation Conditions and Exploration Prospect at × Block in Gabon

加蓬×区块钻遇的最老地层是上白垩统,自下而上分为Azile组、Anguille组、Pointe-Clairette组及Point-Gentile组。上覆新生界主要分布于工区的西南部,地层比较齐全,工区东北部大部遭受剥蚀。Anguille组为半深海相泥岩夹粉细砂岩,分布全区,是主要的产油层之一。Pointe-Clairette组按岩性划分为上下两段(上PC段和下PC段),它们也是重要的产油气层。工区存在上白垩统Azile组和下白垩统Madiela组,N′Toum组三套烃源岩。区域盖层主要包括Anguille组和下PC段的海相泥岩;下白垩统盐岩也是一套十分优质的区域盖层。工区有四套储盖组合,主要为自储自盖和下储上盖。油气藏类型有(断裂)背斜油气藏、断裂鼻状构造油气藏、断块油气藏等。已有8口井在上、下PC段和Anguille组获得工业油气流,控制含油面积5.4km2,石油地质储量352.1×104t,预测含油面积26.4km2,石油地质储量4102.8×104t。在上、下PC段和Anguille组等三个地层中共识别出构造圈闭62个,圈闭总资源量约5×108t。

The Upper Cretaceous Azile, Anguille, Pointe-Clairette and Point-Gentile Formations are the oldest strata drilled at the X Block in Gabon. The overlying Cenozoic rocks are mostly distributed in the southwest part of the block and nearly denudated in the northeast part. Dark Anguille bathyal shale distributed in the whole area the one of the oil pay horizon. PointeClairette Formation includes the upper P.C. and lower P.C.,which are also the main pay horizons. Source rocks are Upper Cretaceous Azile and Lower Cretaceous Madiela and N＇Toum formations. Regional caprocks include Anguille and lower P.C. marine shale as well as the good Lower Cretaceous salt rock. There are four reservoir-cap plays. Reservoir types are faulted/ anticlinal, nose-like faulted, fault-blocked and so on. 62 traps are identified and 10 wells have been drilled in Anguille and the upper and lower P.C strata, among which 8 wells have produced economical oil. It is predicted that there are 26.4 km^2 of oilbearing area and 4102.8×10^4t of original oil in place.