东非裂谷Tanganyika地堑石油地质特征和勘探潜力分析

Geological conditions and exploration potential of Tanganyika Basin in East Africa Rift Valley

随着东非裂谷乌干达区块的勘探获得重大突破,与之石油地质条件相似的Tanganyika地堑的勘探潜力受到了人们的重视。Tanganyika地堑地处东非,属于东非裂谷西支的中段,是典型陆内裂谷盆地,主要沉积中新世以来的地层,现仍大部分被湖水覆盖,湖盆水体较深。盆地整体分为2个次盆,呈三隆夹两凹的构造格局。盆地目前勘探程度较低,根据现有资料推测,盆地地层埋深较大,深洼区中新统地层发育成熟烃源岩,具有较大的生烃潜力和生烃规模;陆内盆地物源相对充足,储盖组合条件较好;应力复杂,能够形成大量多种类型构造及构造-地层圈闭;各种成藏条件匹配关系较好,有利于油气聚集成藏。综合分析认为,盆地具有较大勘探潜力,其中盆地转换带是最有利的油气勘探区。

With the great breakthrough of the exploration for oil and gas in Uganda block of East Africa RiftValley, more attentions are paid to Tanganyika Graben exploration potential as its petroleum geological conditionsis similar to Uganda block. Tanganyika Graben locates in East Africa and is the middle part of western branch ofEast Africa Rift Valley. It is a typical continental rift basin filled by sediments from Later Miocene and currentlycovered by Lake Tanganyika which is a deep fresh lake. The entire graben can be divided into two sub-basins andtakes on the structure framework of two depressions surrounded by three uplifts. Although it is a low explorationbasin, it can be inferred that the mature source rock should insisted in the deep area and has relatively largepotential and scale. As an inland lake, the provenance is relatively sufficient so the reservoir and seal condition isgood enough. Since the multi-stages tectonic alternation, the structural traps can be found in a large amount. Inconclusion, most of the conditions are tend to form effective reservoirs and there is a large potential for explora-tion. The transformation zone of basin is the best area for petroleum accumulation.