关键词: 西非, 被动大陆边缘盆地, 原型盆地, 大油气田, 成藏模式

Abstract:

Based on plate tectonics, using IHS Energy Information Database and  evaluation data of new projects, starting from the prototype basin research of West African passive continental margin basins, the conditions and main controlling factors of the formation of major oil and gas fields in this area, are systematically analyzed. Three kinds of oil and gas accumulation models of major oil and gas fields are established. West African experienced three prototype stages: Early Cretaceous Neocomian to Barremian intracontinental rift stage, Aptian intercontinental rift stage and passive continental margin stage since Albian, respectively filled by continental facies, transitional lagoonal facies and drift stage marine facies. Intracontinental rift lacustrine facies and drift stage marine facies formed two sets of premium source rocks. Transgressive glutenite facies developed in the early transitional period and carbonatite, delta facies and deep water turbidite sandstone facies developed in drift stage, are high quality reservoirs. Salt rocks developed in late transitional period and marine shale developed during drift stage act as high efficiency regional seals respectively for oil and gas fields beneath and over the salt rocks. Accordingly, we established three kinds of oil and gas accumulation models, which are rift type with little salt rocks in the southern region, double layer type with abundant salt rocks in the middle region and high constructive delta type in the northern region. This research not only deepens the understanding of hydrocarbon enrichment rules in West African passive continental margin basins, but also can help to evaluate new projects in this area.

Key words: West Africa, passive continental margin basin, prototype basin, giant oil and gas field, accumulation model of oil and gas