The effect of salinity on in-situ generated CO₂ gas: Simulations and experiments

Carbon dioxide (CO₂) injection has been used as a commercial process for enhanced oil recovery (EOR) since the 1970's. Recently, a new in-situ CO₂ gas generation technology has been developed but not well studied. We conducted experiments to observe the dynamics of the system with different temperatures, injection sequences of chemical agents, chemical additives, and behavior of CO₂ generation with respect to these varying factors and comparison of the actual CO₂ pressure with the calculated values. Experiments on generation of CO₂ gas as a result of reactions of gas forming and gas yielding solutions were carried out. It is shown that the injection sequence of the chemicals affects the reaction characteristics, but the total amount of CO₂ gas generated does not vary significantly. Regardless of the injected solution (either gas forming or gas yielding) the maximum attainable pressures are less than the calculated pressures as a result of chemical equilibrium in the system; so this difference should be considered while calculating the size of the slug in the field applications. The brine concentration has an impact on CO₂ solubility in water and so on CO₂ pressure. Because of this impact, brine concentration of formation water should be considered in addition to the brine which is introduced to the system by the reaction.