东非裂谷Rukwa盆地石油地质特征与勘探潜力

PETROLEUM GEOLOGY AND EXPLORATION POTENTIAL OF RUKWA BASIN IN EAST AFRICAN RIFT SYSTEM

随着东非裂谷西支Albertine盆地勘探获得突破,使该区成为研究和勘探的热点地区。Rukwa盆地作为东非裂谷系中沉积厚度最大的盆地,勘探程度很低。盆地为半地堑结构,位于Tanganyika-Rukwa-Malawi剪切带上,具有走滑拉分的性质。发育二叠系—三叠系Karoo地层、白垩系—古近系Red Sandstone和上新统—更新统Lake Beds三大套地层,沉积地层总厚度最大可达11km,且横向变化很大。盆地内发育Karoo煤层或黑色页岩和Lake Beds湖相泥岩2套潜在的烃源岩。盆地东南部地层埋深大,具备较好储盖组合条件,断层发育,圈闭和油气运移条件较好,推测为有利勘探区。烃源是盆地勘探最主要的地质风险。

Since the breakthrough in oil and gas exploration in the Albertine Basin, the Western Branch of East African Rift System （EARS） has become a hot spot for research and exploration. A- mong the basins in EARS, the Rukwa Basin is the one with thickest deposits but low exploration degree. It is a pull-apart half graben characterized by strike-slipping, located in the Tanganyika-Rukwa- Malawi transform zone. There are three sedimentary sequences in the basin, i.e. the Permian-Triassic Karoo Super-group, the Cretaceous-Paleogene Red Sandstone group and the Pliocene-Pleistocene Lake Beds respectively. The maximum thickness of total deposits may reach 11 kilometers with great horizontal variation. There are two potential source rocks, the Karoo （coal and black shale） and the Lake Beds （lacustrine mudstone）. Good reservoir-seal combination and good hydrocarbon accumulation conditions with well developed fracture system has been found in the southeast, the favorable exploration area of the basin. Source rock is the main geological risk of the exploration in this basin.