Evaluating Injectivity Index of Niger Delta Reservoirs for CO2 Geological Sequestration

Underground storage of carbon dioxide (CO2) has been recognized as a viable strategy to reduce CO2 emissions in the atmosphere. In this context, numerical reservoir simulations are routinely implemented to predict the performance of the project under different operational scenarios and uncertainties. However, numerical simulators are intensive in terms of cost, computational time, and data requirement, thus limiting its use for early commercial applications especially for feasibility studies or quick evaluations. This paper presents the application of a simplified modelling approach to predict dimensionless pressure build-up and injectivity index based on an analytical model for reservoirs in Niger Delta. Data from four (4) Niger Delta reservoirs such as relative permeabilities, reservoir pressure, brine viscosity, and injection rate, among others were used in this work. A modified version of the physics-based model of Mishra et. al was used for conducting the studies. Therefore, equations governing the dimensionless pressure build-up and injectivity index were used to investigate the reservoir and operational characteristics of the well injection of CO2 in Niger delta reservoirs as an alternative to full-field numerical simulation. The model approximates the CO2 injection rate for a given target pressure differential or alternatively, the pressure differential that would result from injecting CO2 at a target rate, given the initial permeability, porosity, permeability, and injection rate. The results were used to rank the reservoirs based on suitability to CO2 sequestration, the displacement efficiency of the CO2 and potential storage in the reservoir. This approach is the first one carried out in the Niger Delta and provides the chance to assess the performance of CO2 storage capacity as a strategy to combat global warming from Nigeria.