A report of Semliki Basin Field Study in Karugutu, Ntoroko District, Western Uganda.

Abstract

Semliki basin is one of the most prospecting basins for petroleum exploration in Uganda. Available data shows the presence of a petroleum system. Thus a field exercise was carried out in this area (Kibuku ) with a major aim of collecting and interpreting stratigraphic, petrographic, sedimentlogic and structural data; which are very important in hydrocarbon exploration. This report comprises a detailed compilation of findings from the basin field study in the Albertine area, Western Uganda. The materials and methodology used to achieve the main objective; collection and interpretation of stratigraphic, petrographic, sedimentologic and structural data, have been outlined and discussed in a single chapter and the study results and interpretations as well as discussions and conclusions about the petroleum system of the study area clearly presented in the succeeding chapters that is a clear differentiation of the lithology and stratigraphy of the basement rock and that of the overlying sediments, an integration of basin analysis concepts in interpretations, facies analysis elements and facies analysis interpretations from observed lithologic units, structures in the basement rock and sediments as well as geophysics of the basin. Semliki basin is generally filled with Middle Miocene to recent age sediments exhibiting a fining upward sequence (characteristic of fluvial systems) from conglomerates (overlying the basement rock) to sands to silts to clays. It is structurally wedge shaped and majorly comprises faults, joints, laminations and bedding planes, cross beds, foliations, quartz veins, unconformities, soft sediment deformation structures among others. The southern part of this basin has the highest elevation but the smallest thickness of accumulated sediments whereas the depocentre (5km thickness of sediments) is in the northern part of the Semliki basin.The sediments in the basin represent a petroleum play for hydrocarbon accumulations, in which the necessary elements of a valid petroleum system were identified as evidenced by the abundance of excellent reservoirs, regionally mature source rocks, traps, intraformational and regional seals as well as hydrocarbon-migration pathways in the basin.