Modeling the effects of completion techniques and formation heterogeneity on CO2 sequestration in shallow and deep saline aquifers

This work studied the effect of completion techniques and reservoir heterogeneity on CO2 storage and injectivity in saline aquifers using a compositional reservoir simulator, CMG-GEM. Two reservoir models were built based on the published data to represent a deep saline aquifer and a shallow aquifer. The effect of various completion conditions on CO2 storage was then discussed, including partial perforation of the reservoir net pay (partial completion), well geometry, orientation, location, and length. The heterogeneity effect was addressed by considering three parameters: mean permeability, the vertical to horizontal permeability ratio, and permeability variation. Sensitivity analysis was carried out using iSIGHT software (design of experiments) to determine the dominant factors affecting CO2 storage capacity and injectivity. Simulation results show that the most favorable option is the perforation of all layers with horizontal wells 250-300 m long set in the upper layers. Mean permeability has the most effect on CO2 storage capacity and injectivity; k(v)/k(h) affects CO2 injectivity storage capacity more than permeability variation, V-k. More CO2 can be stored in the heterogeneous reservoirs with low mean permeability; however, high injectivity can be achieved in the uniform reservoirs with high mean permeability.