Reservoir Characterisation and Modelling for CO2 Sequestration in ‘‘Han’’ Field, Onshore Niger Delta, Nigeria

Abstract

Geoscientists working in the oil and gas industry have a crucial role in combating climate change. In particular, by carrying out regional and local characterization and field projects to demonstrate that different types of geologic storage reservoirs distributed over different basins can permanently and safely store CO2. Therefore, this work is aimed at determining the storage capacity, injectivity, and containment of the reservoir intended for CO2 sequestration. Well logs and 3D seismic data were used to analyze a depleted oil field, (the “HAN” field), in the Niger Delta, Nigeria. Petrophysical analysis was done on the well logs to estimate the net thickness, porosity, water saturation, and injectivity of the reservoirs. Structural interpretation was done on the seismic data, and the volumetric method was used to estimate the storage capacity of the delineated reservoirs. The fault's sealing capacity was determined, and the resulting containment of the reservoirs was estimated. Two sand reservoirs, RES 1 and RES 2, of average thicknesses of 79 m and 93 m, respectively, were delineated across the three analysed wells. The reservoirs effective porosity was 18% and 19%, respectively, and water saturation was 18% and 35%, respectively. The storage capacity of RES 1 was estimated to be 28 MT, and RES 2 was 22 MT. The assessed storage capacity for both reservoirs gave “HAN” field a total storage capacity of approximately 50 MT. The injectivity for RES 1 and RES 2 was determined to be 337 mD and 323 mD, respectively. Based on the threshold set by the International Energy Agency, parameters obtained were observed to be greater than 10 m, 10%, 10%, 200 mD, and 4 MT for thickness, effective porosity, water saturation, injectivity, and storage capacity, respectively. The Han field is suggested as a good field for CO2 sequestration. Furthermore, the Shale Gouge Ratio (SGR) was estimated to be 29% (poor sealing zone) and 44% (moderately sealing zone) in Fault F9 for regions with RES 1 and 2, respectively, to validate their containment. It is evident from the SGR that F9 can serve as a barrier to the migration of CO2 away from the reservoir at deeper depths.