穆格莱德盆地形成特点与勘探潜力

THE DEVELOPMENT FEATURE AND HYDROCARBON EXPLORATION POTENTIAL IN MUGLUD BASIN

穆格莱德盆地形成演化可分为 3期 :(1)早白垩世早期 ,随着非洲南美泛大陆裂开 ,在穆格莱德产生了第一期伸展断陷盆地 ;(2 )早白垩世晚期到晚白垩世 ,随着原始大西洋的产生 ,形成了第二期伸展断陷盆地 ;(3)新生代 ,随着区域沉降 ,该断陷盆地演化为伸展坳陷盆地。晚白垩世末 ,在穆格莱德盆地南部有明显的挤压运动 ,形成构造反转 ;在盆地西北侧 ,沿中非大断裂带有走滑运动 ,使得图卢斯、巴加拉凹陷受到强烈的改造。穆格莱德盆地主要构造样式有半地堑、半地垒 (或地垒 )、伸展断块、滚动背斜、反转形成的挤压背斜和走滑活动形成的负花状构造等。滚动背斜、挤压背斜、地垒等构造是油气富集的主要场所。早白垩世早期充填了半深湖深湖相的泥岩 ,控制了烃源岩的分布。由于沉降中心不断向南转移 ,在南区沉积了上白垩统优质的厚层泥岩 ,形成了大油田的区域盖层。上述地质条件决定了穆格莱德盆地具有良好的勘探前景。

The development and evolution of Muglud basin can be divided into three stages: (1) in the early Cretaceous, with the Africa-South America continent splitting, the first extension downchasm basin ocured; (2) in the late Cretaceous, with the original Atlantic Ocean formation, the second extension downchasm basin occurred; (3) in Kainozoic, with the regional subsidence, this basin evoluted into a sag basin. From the end of the late cretaceous, there were apparent movements, resulting in reverse structure. In the west-north basin, there were strik-slip movements along the great central African fracture. As a result, Tullus, Bagarra sub-basins were greatly reformed. The main structural styles of Muglud basin are half graben, half horst(or horst), extension fault-block, rollover anticline, compression anticline and flower structure. Among them, rollover anticline, compression anticline and horst are the main area of hydrocarbon enrichment. In the early Cretaceous, the basin was filled with mudstone of half-abyss and abyss facies, which controlled the distribution of hydrocarbon rocks. As the sediment center continuously moved southwards, good thick upper Cretaceous mudstone deposited in the south area, and formed regional cap-rock of giant oil field.Therefore,good potential region for oil and gas exploration in Muglud basin is decided by the above factors.