Reservoir characterization of Kolmani Field, Northeast Nigeria, using well log data and 3D seismic data for enhanced hydrocarbon prospectivity

Abstract

Kolmani field in the Gongola Basin, Upper Benue Trough, northeastern Nigeria had been underexplored with only three exploratory wells. The source rocks have been proven good; the reservoirs are yet to achieve their potentials. Therefore, this work characterized the reservoirs within Kolmani Field using well log and 3D seismic data for enhanced hydrocarbon prospectivity. The identified aggradational sequences in Kowell-1 well (6536.88ft-8172.75ft) and Kowell-2 well (6413.80ft-8218.78ft) likely formed in a floodplain or shallow marine shelf environment. In contrast, the progradational sequences in Kowell-1 (5690.74ft—6536.88ft) and Kowell-2 (5234.33 to 6413.80 ft) suggest deltaic or shoreline deposits. The retrogradational sequences in Kowell-1 (5101–5690.74 ft) and Kowell-2 (6413.80–8218.78ft) indicate a probable transgressive marine shelf or estuarine environment. However, two wells (Kowell-1 and Kowell-2) were used for petrophysical evaluation. Faults, anticlinal structures, four reservoirs, four complete depositional cycles, one prospect, and two leads were delineated. Reservoir data from the two wells in the Yolde Formation indicated gross thicknesses range from 180.5 to 566.9 ft, with net-to-gross (N/G) ratios between 0.42 and 0.87. V-shale values vary from 0.25 to 0.46, while porosity (Phi) ranges from 0.17 to 0.34. Water saturation (Sw) is between 0.30 and 0.51, with hydrocarbon saturation (Sh) from 0.49 to 0.70. Permeability (K) values range from 400.86 to 900.25 mD, indicating good reservoir quality. The mapped prospect A has 26 BCF STGIIP and 69.47 Mbbl STOIIP. The volumetrics of reservoirs suggest that Kolmani field is a promising field for hydrocarbon exploration.