非洲东西部被动大陆边缘盆地油气分布差异

以板块构造理论为基础,通过分析非洲东西部被动大陆边缘盆地的形成和演化,对比盆地的勘探数据,总结了两个地区的石油地质条件与油气分布差异,并探讨了其成因。非洲东西部共发育30个被动大陆边缘盆地,该类盆地是冈瓦纳大陆裂解,非洲与南北美洲、南极洲、印度分离的产物。板块分离过程的演化差异引起了不同的构造和沉积特征及油气分布差异。西非三角洲盆地和盐拱发育的含盐被动大陆边缘盆地油气资源丰富,尤其是深水区的油气资源量要远远大于东非,这是由于西非盆地形成时发育了巨厚的高品质烃源岩和塑性地层,且上覆有大型水系带来的巨厚碎屑岩沉积物,有利于烃源岩成熟及深水浊积砂岩、同生断层及变形构造圈闭的形成。图5表2参20

Difference in hydrocarbon distribution in passive margin basins of eastern and western Africa

On the basis of plate tectonic theory, we analyzed the formation and evolution of passive continental basins in eastern and western Africa, compared exploration data, and discussed the differences in petroleum geological conditions and hydrocarbon distribution in the two regions. Thirty passive marginal basins have been developed due to the break of Gondwanaland and formed by the African plate breaking away from America, Antarctic and India. They are different in hydrocarbon distribution owing to different tectonic-sedimentary evolution processes. Most hydrocarbon resources were accumulated in salt-containing basins and delta basins of western Africa, especially in deep water, much larger than those in East Africa. In those oil-rich basins of west Africa, thick and high quality source rocks and plastic strata were well developed. In addition, thick overlying sediment supply from Tertiary large water system contributed to high-maturity source rocks and the formation of deep water turbidity sandstones and traps of growth fault and deformation structures.