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ItemA detailed field project report about the Semliki basin in Ntoroko District, Albertine Grabben.(Makerere University, 2026)This report presents the findings of a field study conducted between 8th and 19th June 2025 in the Semliki Basin, located within the Albertine Graben of the East African Rift System (EARS), Ntoroko District, southwestern Uganda. The study was carried out by third-year students of the Bachelor of Science in Petroleum Geoscience and Production programme at Makerere University, under the coordination of the Department of Geology and Petroleum Studies. The Semliki Basin is a half-graben rift structure covering approximately 1,200 km², bounded by the Rwenzori Mountain escarpments to the southeast, Lake Albert to the north, and the Semliki and Lamia rivers to the west. Fieldwork focused on the Kichwamba, Kisegi Hill, Kibuku roadcut, Turaco well sites, and Sempaya Hot Springs, employing methods including stratigraphic logging, structural measurements, grain size analysis, paleocurrent determination, facies analysis, and geophysical data interpretation. Basement lithology consists primarily of high-grade Proterozoic metamorphic rocks including granite gneisses, migmatites, and quartzites, which are heavily jointed and fractured. Overlying these basement rocks are seven Miocene-to-Recent sedimentary formations; the Kisegi, Kasande, Kakara, Oluka, Nyaburugo, Nyakabingo, and Nyabusosi formations; comprising sandstones, siltstones, mudstones, conglomerates, and clays deposited in fluvial, deltaic, and lacustrine environments. Structural analysis revealed NE-SW-trending normal faults, joints, foliations, and folds consistent with the extensional tectonics of the Albertine Graben. Primary sedimentary structures including cross-bedding, laminations, ripple marks, and mud cracks were used to reconstruct paleocurrent directions and depositional environments. Geophysical studies, including Bouguer gravity anomaly maps, total magnetic intensity maps, seismic section interpretation, and petrophysical wireline log analysis from the Turaco 1, 2, and 3 wells, confirmed the basin's asymmetric half-graben architecture and the presence of hydrocarbon-bearing intervals. The Semliki Basin demonstrates all the critical elements of a viable petroleum system: lacustrine source rocks with significant organic content (Kasande Formation), porous and permeable sandstone reservoir rocks (Kisegi Formation), impermeable clay top seals, and structural and stratigraphic traps associated with the basin's fault architecture. Evidence of active oil generation is provided by the Kibuku oil seep, while the Sempaya Hot Springs in the Buranga Geothermal Field indicate elevated geothermal gradients that accelerate source rock maturation. Overall, the Semliki Basin holds substantial potential for hydrocarbon exploration, warranting continued geological and geophysical investigation.
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ItemSemliki basin field study report(Makerere University, 2026)This study presents observations from a comprehensive field excursion conducted in the Semliki Basin, situated within the Albertine Graben of Western Uganda. The primary objective of the excursion was to gain a deeper understanding of the formation, sedimentary environment and petroleum potential of the basin. Throughout the fieldwork, various sites within the basin were studied, including locations such as Kichwamba, Kisegi hill quarry, Kisegi River, Kibuku road cut, and Sempaya hot springs. Through detailed fieldwork and data collection using GPS and geological tools, the students aimed to achieve several specific objectives. These objectives included identifying lithologies present in the Semliki basin, analyzing and correlating structural features observed within both the basement and sedimentary layers, assessing different elements of the petroleum system, and identifying various facies and depositional environments. During the fieldwork, an extensive range of facies was logged and analyzed. These included fluvial, deltaic, and lacustrine sediments, all of which were significantly influenced by intensive tectonic activity within the basin. The sedimentary structures observed encompassed a diverse array, including cross-bedding, unconformities, faults and deformation bands. Of particular interest was the presence of hot springs within the area, indicating a notable geothermal gradient, which holds significant implications for source rock maturation and potential hydrocarbon generation. The integration of sedimentology, stratigraphy, and tectonics facilitated a comprehensive interpretation of the basin's geological history and provided valuable insights into its economic importance.
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ItemGeologic and stratigraphic logging report of the Semliki Basin Albertine Graben in ntoroko.(Makerere University, 2026)This report presents a comprehensive geological and stratigraphic study of the Semliki Basin, a half-graben within the western arm of the East African Rift System (EARS), located south and east of Lake Albert in Ntoroko District, Western Uganda. The basin has its shallow end in Uganda and deeper end in Congo, and sediment thickness exceeding 6 km. The field study was conducted as a field training exercise for fourth-year Petroleum Geoscience students at Makerere University targeting areas like Kichwamba, Kibuku Quarry, Itojo, Makondo Fault, and the Turaco well site. It aimed at building skills in lithological description, stratigraphic logging, facies analysis, structural interpretation, and geophysical data assessment, while investigating the basin’s depositional environments, sedimentological processes, sequence stratigraphy, and petroleum potential. Its basement of the Semliki basin consists of high-grade metamorphic rocks like granitic gneisses and migmatites, overlain by sedimentary sequences classified into seven formations based on lithological characteristics and age. These include Kisegi, Kasande, Kakara, Oluka, Nyaburogo, Nyakabingo, and Nyabusosi (Lukaye, 2016). Stratigraphic logs revealed fluvio-lacustrine sequences, including sandstones, silts and clays, with fining-upward and coarsening-upward sequences, cross-bedding, cross-stratification, and blocky clays, indicating deposition in fluvial-deltaic to lacustrine settings influenced by intense tectonic activity. Tectonic forces formed diverse structures, including faults, joints, bedding, laminations, mud diapirs, plunging folds, and normal faulting, observed on outcrops. Geophysical data, including magnetic and gravity surveys, confirmed the basin’s sedimentary nature, while petrophysical analysis of the Turaco-2 well identified moderate-quality sandstone reservoirs interbedded with thick clays and evaporites, suggesting reservoir potential. The presence of Sempaya hot springs and oil seeps in the Kibuku area indicates a high geothermal gradient and organic-rich source rocks, supporting source rock maturation and an active petroleum system. The study confirms the Semliki Basin contains all essential components of a petroleum system including source rock, reservoir, structural traps, and seal. Future exploration should prioritize high-resolution 3D seismic surveys, basin modeling, and geochemical analysis to assess gas origins and trap viability. The basin’s geothermal potential, driven by high heat flow and active faulting, also warrants further investigation.
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ItemA report on the geologic and stratigraphic logging project of the Semliki basin in the Albertine Graben, Ntoroko District, Western Uganda(Makerere University, 2025)The Semliki Basin, located in the western branch of the East African Rift System, includes the Kibuku area and is part of Block 3 of Uganda‘s Albertine Graben under a Petroleum Exploration License. This basin is shared by Uganda and the Democratic Republic of the Congo. The Ugandan portion lies in the southern part of Lake Albert and the adjacent land to the south. The geological foundation beneath the rift (the pre-rift basement) is made up of both felsic and mafic rocks. After the rift formed, the overlying rock layers (post-rift lithology) included altered granites, granitic gneisses, and sedimentary rocks—mainly deposited by rivers and lakes. Both types of rocks are thought to have originated from the nearby Rwenzori Mountains. Stratigraphically, the sediments are classified into five main formations. From oldest to youngest, these are the Kasande (bottom), Nyaburogo, Oluka, Karaka, and Katorogo (top) formations. Studies of the basin and sediment types suggest that the Kibuku area‘s sediments, especially those exposed along road cuts, were deposited in environments such as rivers, lakes, and deltas. Pebbles found in the conglomerates that rest on the basement rocks closely match the mineral composition of the Rwenzori Mountains, indicating that the sediments likely came from there. The Semliki Basin is considered a potential petroleum system, showing essential features for oil accumulation: possible reservoirs, source rocks, seals, traps, and migration routes for hydrocarbons. It is a sub-basin within the broader Albertine Graben, which is Uganda‘s most promising region for oil and gas exploration. The basin holds sediments from the mid-Miocene to the present, lying over older layers that may date back to the Jurassic or Early Tertiary, and these rest unevenly on the basement rocks. The main types of sediment in the basin are sandstones, siltstones, and claystones, mostly deposited by rivers, lakes, and deltas. The basement consists of igneous and high-grade metamorphic rocks like granites and granite gneiss. To evaluate the petroleum potential of the basin, detailed structural and stratigraphic data were collected and analyzed. Due to significant tectonic activity in the region, both the basement and sedimentary rocks display a variety of geological features, including folds, bedding planes, cross-bedding, unconformities, joints, veins, and faults. The early development of oil-generating organic matter in these young sediments is supported by surface features like the Sempaya Hot Springs. Overall, the Semliki Basin has been confirmed as a potential petroleum play, with all the critical elements of a functioning petroleum system in place
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ItemA field study project report of the Semliki Basin in the Albertine Graben of Western Uganda(Makerere University, 2026)This project report provides an in depth of the Field exercise (geologic and stratigraphic logging) carried out in the Semliki basin of the Albertine graben. The main objective was to obtain field training on how to collect and interpret stratigraphic, petrographic, sedimentologic and structural data; which are very important in hydrocarbon exploration. The other objective is to identify the facies and depositional environments. The materials that were used in the field include; grain size scale, tape measure, Jacob staff, compass, hand lens and a geological hammer. The basement lithologies identified include; granitic gneiss and migmatite while sediment lithologies observed include sands and clays. The Semliki basin is composed of both primary and secondary structures. The primary structures observed include; planar bedding, mudcracks and stratification while secondary structures were joints, folds, foliations, quartz veins and faults. The general trend of these structures was found to be in NE-SW direction that was consistent with tectonic forces that affected the Semliki Basin. The facies and basin analysis revealed three depositional environments; lacustrine, fluvial and deltaic that occurred in the Semliki basin basin. Sedlog software was employed to generate group Flog and a combined log for the different groups. Through geophysical studies Semliki basin, sedimentary basins were identified through analysis of magnetic and gravity the datasets using GeoSoft/Oasis Montaj software. Techlog software was also used to analyze well log data from Turaco-2 well which revealed gas filled sand formation. The findings from the field exercise reveal a good potential for hydrocarbons in the Semliki basin through presence of good quality reservoir sands, potential lacustrine clay source rocks, traps and migrating pathways formed by the structural and stratigraphic deformation of this basin.