GEOCHEMICAL SIGNIFICANCE OF SEEPAGE OILS AND BITUMINOUS SANDSTONES IN THE ALBERTINE GRABEN, UGANDA

Although Uganda has a long history of surface petroleum exploration, no commercial oilfields have yet been found there. The most prospective area in the country is the Albertine graben (Fig. 1); this is 570km long and about 45km wide, and extends into the Democratic Republic of Congo. Previous geological and geophysical studies have concluded that mature source rocks are present in the graben, and the presence of an active petroleum system is indicated by the occurrence of oil seeps. Wayland (1925) identified oil and gas shows at 52 locations within and around Lake Albert. At the present day, surface seepages of petroleum occur at Paraa, Kibiro and Kibuku (see Fig. 2). The existence of these seepages indicates that not only are effective source rocks present, but also that they have generated and expelled oil and that migration has taken place. In order to investigate the petroleum potential of the Albertine graben, CNODC geologists have recently participated in a joint research programme with PEPD Uganda. Three seepage oils, two bituminous sandstones and five shales were collected for organic geochemical analysis (Table 1). Sample locations are shown in Fig. 2.