Petrophysical analysis of Chela pre-saliferous and Kinkasi post-saliferous reservoirs in the onshore coastal basin of the Democratic Republic of Congo (DRC)

The Chela (Barremian) and Kinkasi (Cenomanian) formations contain important hydrocarbon-bearing reservoir intervals within the onshore Democratic Republic of Congo (DRC) Coastal Basin. However, despite favorable geological conditions and the recognized hydrocarbon prospectivity of these reservoirs, hydrocarbon production remains limited and restricted to the Lindu-1 well. Consequently, reservoir continuity, hydrocarbon distribution, and overall production potential within the Nganzi, Yema, and Matamba-Makanzi (YMM) blocks remain insufficiently characterized. This study aims to quantitatively evaluate the reservoir properties and hydrocarbon potential of these formations through the integrated analysis of well-log data acquired from fifteen wells. Well correlation was conducted using Frac-Predictor, while petrophysical parameters including porosity, shale volume, water saturation, and lithology were analyzed using Interactive Petrophysics (IP 4.1). The Chela reservoir, in the pre-salt section, shows thicknesses of 9–74 m, shale content of 15–52%, porosity of 12.65 to 32%, water saturation of 24.4 to 36.8%, and hydrocarbon saturation of 63.2–75.6% derived solely from the Bayingu-1 and Lindu-2 wells. The Kinkasi reservoir, in the post-salt section, ranges from 29 to 419 m in thickness, with shale content of 30–47%, porosity of 15–24%, water saturation of 37–86%, and hydrocarbon saturation of 14–62.7%. Stratigraphic variations strongly influence hydrocarbon distribution. Nganzi lacks most post-salt formations, whereas the YMM blocks contain thin or absent Chela intervals but extensive Kinkasi formations near productive areas in the Perenco concession and neighboring countries. Only Lindu-1 produced oil (2,617 barrels), indicating challenges with reservoir continuity, hydrocarbon migration, and well placement. These results suggest the YMM blocks remain prospective, although confirmation of trap integrity, seal, and migration requires further structural and seismic evaluation.