Fluvial geomorphology of the Turaco prospect, Semliki basin, south-western Uganda

Abstract

Turaco Prospect was identified in the Semliki Basin located south of Lake Albert. Turaco-1, 2 and 3 wells were drilled by Heritage Oil and Gas Limited (HOGL) in 2002, 2004 and 2005 respectively and the location selected on the basis of a 2-D seismic dataset. Although the three (3) wells were largely unsuccessful, the Turaco-3 well which was drilled to a Total depth (TD) of 2960m encountered hydrocarbon bearing Formations. A 3-D seismic data was later acquired in 2005 over the Turaco Prospect area but was not significantly utilized to better understand the Prospect. This research utilized attributes derived from the 3-D seismic and well data that exists over the Turaco Prospect, RGB blending and geobody extraction to study the fluvial geomorphology of the area. The four (4) 3-D seismic attributes, namely; RMS amplitude, Sweetness, Variance and Envelope have been evaluated and used in the analysis of facies and depositional environment in the basin together with Gamma Ray well logs. Four seismic events or horizons were picked and interpreted. The choice of the seismic events was based on the quality of the seismic-well ties along with interpretive judgment on the reservoir targets that have been well defined bythe Turaco-1, 2 and 3 wells. The Formation s interpreted were the Nyaburogo, Oluka, Kakara and Kisegi. The seismic attribute maps for the different Formation s were generated using different extraction methods in petrel software; this was followed by RGB blending and geobody extractions to create maps for interpretation and analysis to identify seismic facies, depositional environment and their lateral variation. Eight (8) primary facies associations have been identified and interpreted. These are Crevasse Channels, Distributary Channels, Mouth Bars, Bifurcation Bars and Point Bars which are associated with Fluvial Environment as per the grouping and interpretation from Gamma Ray log interpretation, and Delta Front, Lower Delta Plain and Upper Delta Plain which are associated with the Delta and Lacustrine Environments also as per the grouping and interpretation from Gamma Ray log interpretation. The mapping and inference of facies from seismic attribute maps was entirely based on the variation in attribute values which is depicted by colors after RGB color blending. From the attribute maps, three sediment lithologies have been interpreted that is: sands, silts and clays