Geologic and stratigraphic logging project in Semiliki Basin-Albertine Graben Ntoroko District Western Uganda

Abstract

The Semliki Basin is covered by sediments that represent the Middle Miocene to recent, which are described from outcrops and well data, underlain by possible Jurrassic or Permo-Triassic to early tertiary sediments which rest unconformably on the basement rocks. Sediments in Semliki basin are predominantly composed of sandstones, claystones and siltstones while the basement rocks consist of high grade metamorphic and igneous rocks such as granite, granite gneiss, amphibolite and quartz veins. The study has allowed a better understanding of the stratigraphic relationship of the different rock units that are exposed on the outcrops and those interpreted from well data. The depositional environment of the sediments in the Semliki basin is fluvial-lacustrine/deltaic showing significant variations in gamma ray character, which reflect the water level changes and river interactions through the depositional period and the influence of rifting tectonics on the sediment deposition throughout time and space. The surface manifestation of Sempaya Hot spring is evident for the early maturation of the organic matter to expel oil in the young sediments of the Albertine graben. The sediments in the Semliki basin represent petroleum play for hydrocarbon accumulations, in which the necessary elements of a valid petroleum system were identified. These include excellent or good potential reservoir rocks and seals as well as circumstantial evidence of regionally mature source rocks, possible seals, traps and hydrocarbon-migration pathways.