A report on a geologic field project in Semilik basin area, Ntoroko district.

Abstract

As students pursuing Petroleum Geosciences and Production program, we are required to do fieldwork and excursion study in the Albertine Graben under the guidance of our lecturers during the recess term of third year of our study for fourteen days. The area of study was Semliki basin located in the southern part of the Albertine Graben (Ntoroko district) western Uganda. Semliki area lies onshore south of Lake Albert, it is bounded by the escarpment to the east and south and by rivers Lamia and Semliki to the west. It covers approximately 1200km². The aim of this study was to enable us apply the geological, geophysical and other knowledge we have acquired during the course of the program to understand the geology, scrutinize and analyze the petroleum system of the area practically, also study the environments of deposition and the depositional processes that took place in the area. We collected vast structural and stratigraphic data that we then analyzed to make conclusions about the petroleum potential of Semliki basin. The study area comprised of fluvial, deltaic and lacustrine sediments. The basin was affected by intensive tectonic activity, which led to the formation of vast types of structures with in the basement and sediments that we observed, examples of these structures include faults, joints, folds, veins and banding. Sedimentary structures observed included cross bedding, unconformities, faults, a mud diapir and deformation bands. Mud diapirs, faults, plunging folds would be good structural seals. The presence of hot springs with in the area indicated the presence of high enough geothermal gradients for maturation and expulsion of hydrocarbons. Sedimentology, stratigraphy and tectonics are applied to develop a full understanding of the rocks and the sediments that fill Semliki sedimentary basin and use this information to interpret the geologic history and evaluate the economic importance of these rocks. We concluded that the study area had a good (working) petroleum system characterized with all the required system components that is source rocks reservoir rocks, seals, traps and migration pathways.