Application of polymer-gel solutions in remediating leakage in CO₂ storage reservoirs

The application of crosslinked gels has seen widespread use within the petroleum industry to divert fluid flow and remediate leakage at wells. The current study aimed at investigating the effectiveness of polymer-gel treatment in remediating a potential CO₂ leakage site in the subsurface. This paper presents a brief summary of the results of laboratory characterisation work carried out on polymer gels, which involved characterisation of several polymer-gel systems with respect to their working and gelation times and conducting core flooding experiments on reservoir rocks to characterise their permeability reduction behaviour. The chemical flooding reservoir simulator, UTCHEM, was used to simulate polymer injection and its subsequent gelation process in the saline aquifer model. Parameters such as polymer concentration, polymer to crosslinker ratio and pH, and their influence on the gelation process and the area of influence have been investigated. The results have shown that lower polymer to crosslinker ratios lead to a relatively higher gel concentration. On the other hand, higher polymer to crosslinker ratios result in a relatively higher area of influence, which is mainly due to the decreased viscosity and slower gelation rate. It was also found that, as the concentration of H⁺ in the injection stream increases, the rate of crosslinking decreases and the lower viscosity polymer slug migrates to the far-field region of the reservoir formation.