Hydrocarbon Potential of the Semliki Basin in the Albertine Graben, Uganda

Abstract

The Semliki Basin is situated in the Albertine Graben in Western Uganda. It has a total area of approximately 740 km2 and comprises of three (3) Petroleum Exploration Blocks (Block 3B, 3C and 3D). Geophysical surveys suggest a maximum of 6 km sedimentary succession in the basin. Three wells have been so far drilled in the semliki Basin on the hanging wall of the Makondo Fault. The wells penetrated almost 3,000 m of the sedimentary sequence without intersecting basement. Gravity, magnetic and seismic data acquired in the area show that the main structural elements in the Semliki Basin are faults, grabens and horsts formed as a result of tensional stress. It also shows that the basin is characterized by multi-stacked good quality reservoirs associated with growth and flower fault related structures. Areas of gravity lows generally have greater sedimentary thickness. The geology is such that alluvial fans and deltaic facies interfinger with lacustrine facies thereby providing excellent reservoir capabilities. Potential structures for hydrocarbon accumulation include normal faults, strata in alluvial fans, and fractured basement blocks. There are also several oil seeps in the basin. Organic geochemical studies on potential source rocks show that the source rocks are of clastic facies, organic rich, oil-prone (type II kerogen), thermally mature (within peak oil generation) with good oil generative potential. The above integral study generally suggest that the Semliki Basin has good prospects for hydrocarbon plays, with high potential for both structural and stratigraphic traps. It should also be noted that the tectonic, stratigraphic and organic geochemical evaluations suggest similarity of the Semliki Basin with the contiguous basins of Southern Lake Albert, Northern Lake Albert, and Pakwach Basins, where commercial oil discoveries with STOIIP of 6.5 billion barrels of oil have been made. The Semliki Basin correlates closely with these basins in temporal disposition, structures, source and reservoir rocks and probably also generation mechanism. The Semliki Basin therefore provides attractive opportunities for oil and gas exploration and development. So far, out of the 3 exploration blocks within the Basin, only one block is under an exploration license by an International Oil company. Key words: Semliki Basin, geophysical, geological & geochemical data, hydrocarbon potential

AAPG Datapages/Search and Discovery Article #90332 © 2018 AAPG International Conference and Exhibition, Cape Town, South Africa, November 4-11, 2018