CONTRIBUTION TO THE GEOLOGICAL AND PETROLEUM STUDY OF THE WEST-CONGOLIAN BASIN – CASE OF CARBONATES IN THE KITOBOLA REGION IN CENTRAL CONGO, D.R. CONGO

Previous studies carried out in the West-Congolian basin have highlighted potential formations that could play a major role in a petroleum system. In order to complete and enrich the geological and petroleum dossier of the said basin, a field trip to the Kitobola locality in the province of Central Congo was necessary to sample, analyze and describe the carbonate formations that outcrop there, in order to detect their importance from a petroleum point of view by describing and analyzing their mineralogical characteristics, and geochemical characteristics of these rocks, as well as evaluating their basic petrophysical parameters, notably porosity and permeability, in order to determine the role they might play in a petroleum system. Samples were sent to CRGM laboratories for petrographic, petrophysical and geochemical analyses, which revealed the presence of limestones (mudstones, wackestones and pelmicrite) with low porosity ranging from 1.18 to 1.49% and near-zero permeability between 0.2 and 0.5 mD. Geochemical analyses revealed a TOC ranging from 0.9 to 1.3 and high proportions of calcium oxide CaO associated with the limestones. As a result, these formations cannot be used as reservoirs, but rather as blankets, given their low porosity and near-zero permeability. On the other hand, they would make excellent source rocks in a petroleum system, given their very satisfactory TOC values. This article provides new information on the intrinsic characteristics (petrographic, petrophysical and geochemical) of the carbonate formations outcropping in the Kitobola region of the West Congolian Basin, while also highlighting potential source rocks or blankets.