CO 2 -triggered gelation for mobility control and channeling blocking during CO 2 flooding processes

CO 2 flooding is regarded as an important method for enhanced oil recovery (EOR) and greenhouse gas control. However, the heterogeneity prevalently distributed in reservoirs inhibits the performance of this technology. The sweep efficiency can be significantly reduced especially in the presence of “thief zones”. Hence, gas channeling blocking and mobility control are important technical issues for the success of CO 2 injection. Normally, crosslinked gels have the potential to block gas channels, but the gelation time control poses challenges to this method. In this study, a new method for selectively blocking CO 2 channeling is proposed, which is based on a type of CO 2 -sensitive gel system (modified polyacrylamide-methenamine-resorcinol gel system) to form gel in situ. A CO 2 -sensitive gel system is when gelation or solidification will be triggered by CO 2 in the reservoir to block gas channels. The CO 2 -sensitivity of the gel system was demonstrated in parallel bottle tests of gel in N 2 and CO 2 atmospheres. Sand pack flow experiments were conducted to investigate the shutoff capacity of the gel system under different conditions. The injectivity of the gel system was studied via viscosity measurements. The results indicate that this gel system was sensitive to CO 2 and had good performance of channeling blocking in porous media. Advantageous viscosity-temperature characteristics were achieved in this work. The effectiveness for EOR in heterogeneous formations based on this gel system was demonstrated using displacement tests conducted in double sand packs. The experimental results can provide guidelines for the deployment of the CO 2 -sensitive gel system for field applications.