In order to better circumscribe a petroleum field, several delineation drilling must be carried out to obtain the maximum of the data by using various methods and techniques which will lead to modeling the reservoir to optimize the recovery of its hydrocarbons. Thus, during the drilling of the OKA-01 oil well in the Tshiala (Offshore) field of the DRC coastal basin, the Pinda formation presents an extreme lithological complexity with a combination of siliciclastic carbonate which is associated with a wide variety of environments. We used a method called Gas While Drilling that uses surface-detected gas during drilling for fast determination of valuable reservoir information such as identification and characterization of hydrocarbons in the lower Pinda reservoir, which are the subject and the contribution of this study. The obtained results from this study are represented in graphic form or figures and cross-plots; the latter are analyzed and interpreted according to the different components present in the fluids, that is to say the quantity of the components (C2-C5) to that of the component C1 as well as the rations of Wetness Ratio (Wh); Balance Ratio (Bh) and Character Ratio (Ch). Data collected from our method compared to other methods used during this drilling of the OKA-1 well identified and characterized the heavy oils in the OKA-01 well, indicating a problem of their recovery with primary methods. and secondary; allowing to consider tertiary recovery techniques with a work over project.

Le présent travail a pour objectif de faire une étude structurale du sous-bassin de Busira en se basant sur l’interprétation des cartes d’anomalies gravimétriques. Ce sous-bassin qui est une zone d’intérêt pétrolier majeur, est situé dans la Cuvette Centrale de la R.D. Congo. Les valeurs d’anomalies de Bouguer nous ont permis de localiser des zones de hautes et basses intensités qui correspondraient respectivement à des horsts et des fossés. Notons aussi que les changements abrupts d’intensités et les resserrements des courbes d’iso-anomalies constituent les signatures gravimétriques classiques des failles. Pour mieux étudier notre bassin sédimentaire, nous avons recouru à la méthode de séparation régionale-résiduelle. C’est l’interprétation des cartes d’anomalies régionales qui nous a permis de mieux connaitre la structure du socle de notre bassin sédimentaire. Ces cartes 2D et 3D d’anomalies régionales ont été élaborées en soustrayant les bruits aux anomalies de Bouguer. L’analyse des valeurs d’intensités d’anomalies régionales, de la forme des courbes d’iso-anomalies et des profils tracés sur ces cartes a abouti à la mise en évidence des zones affaissées (fossés ou grabens) et des zones surélevées (horsts) qui sont séparées par des failles. Nous avons aussi recouru, au traçage des profils sur la carte d’anomalies résiduelles et à des corrélations avec les profils sismiques effectués dans ce secteur permettant de déceler plusieurs structures géologiques d’un très grand intérêt pétrolier. L’application des filtres directionnels nous a permis de localiser avec précision plusieurs failles probables ou autres contacts géologiques et d’établir leurs directions préférentielles.

The exploration of the Central sedimentary basin in Democratic Republic of Congo, focused on geological, geochemical and geophysical studies, as well as well drilling, started early in nineteen fifty with several foreign organizations including the Belgian firm REMINA. Coupled with field work carried out by the Congolese national oil company, this work resulted in the confirmation of the surface index at several sites, as well as the recognition of the potential mother rocks, reservoir rocks and cover rocks. In this work we contribute to the development of a geological model of the petroleum system of this sedimentary basin based on the interpretation of Bouguer anomalies. After analysis the results are represented in the form of maps. Apart from the surface index, mother rocks, reservoir rocks and cover rocks already confirmed in this area, these results have enabled the identification of places with large sediment thicknesses or central deposits and areas likely to trap hydrocarbons in this basin. Our model of this sedimentary basin allows to locate the maturation zones of the mother rocks, gives an idea of the direction of hydrocarbon migration, help identification and the location of the probable geological structures favourable to the accumulation of oil in this area.