RESERVOIR HETEROGENEITY AND ITS IMPLICATIONS TO CO2 STORAGE: A CASE STUDY OF THE BIMA FORMATION, NORTHERN BENUE TROUGH, NIGERIA

Subsurface CO2 storage is regarded as one of the reliable technologies presently considered to achieve the net zero emissions target. Here, we present for the first time the Bima Formation as a potential reservoir rock for subsurface CO2 storage. Outcrop sections studied identified depositional facies (e.g. debris flow, gravelly/sandy channels and bars, sheet flood, floodplain, abandoned channel, lacustrine, etc.) interpreted as potential reservoir flow units that could allow efficient migration and potential storage of injected CO2. While the mudstone/shale units of the floodplain, abandoned channel and lacustrine facies could potentially constitute permeability barriers and baffles to the stored CO2. Structural heterogeneities at macro and micro scales evidence from meter-scale-spaced faults and deformation bands which could potentially provide path ways for efficient fluid flow (CO2) within the reservoir. However, such structures could also potentially compartmentalize the reservoir and reduce connectivity limiting its potential for large scale CO2 storage. Diagenetic alteration within the reservoir has resulted in the formation of quartz overgrowth. However, the formation of grain-coating Fe-rich clays like illite and chlorite inhibited the extensive quartz overgrowth, thereby preserving porosity of the formation. Dissolution of feldspars during telodiagenesis has also enhanced the secondary porosity.