Comparison of Completion and Heterogeneity Effect on CO₂ Sequestration in Shallow and Deep Saline Aquifers

The effect of completion techniques and reservoir heterogeneity on CO ₂ storage and injectivity in saline aquifers has been studied using a compositional reservoir simulator CMG-GEM. Two reservoir models were built using data extracted from publications, to represent a deep saline aquifer and a shallow aquifer. The effect of completion methods, including partial perforation of the reservoir net pay (partial completion), well geometry, orientation, location and length, on CO ₂ storage are discussed. Heterogeneity effect has been addressed considering three parameters: mean permeability, vertical to horizontal permeability ratio, and permeability variation. Sensitivity analysis was carried out using design of experiments (DOE) to determine the dominant factors affecting CO ₂ storage capacity and CO ₂ injectivity. Simulation results show that completing all layers, using horizontal wells set in upper layers with a length around 250-300 m are the most favorable choices for CO ₂ storage capacity in the aquifer examined. Mean permeability affects CO ₂ storage capacity and injectivity the most; k _v /k _h affects CO ₂ injectivity storage capacity more than permeability variation, V _k . More CO ₂ 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.