Investigation of Effect of Gas Injection Pressure on Oil Recovery Accompanying CO2 Increasing in Injection Gas Composition

Abstract

Abstract Gas injection is a common EOR method for increasing oil recovery factor. It is an economical method, especially in cases where the injection gas for such gas injection project is easily available. In this study, the performance of gas injection into one of the Iranian reservoirs is investigated. Three sets of core flood experiments were conducted. Each run was conducted at different composition and injection pressure. The results of experiments revealed the fact that the recovery efficiency depends strongly on the injection pressure. It should also be noted that gas enrichment using components leading miscibility could increase the recovery. The optimum enrichment level was also an affecting factor, which controls the overall efficiency of gas injection. In the last phase of this study, the minimum miscibility pressure of the injected gas and in-situ oil under operated conditions was calculated using simulation package. These simulation runs were conducted for different percentage of CO2 in injected gas. Results of these simulation runs were in a good agreement with experimental results. It was found that as the CO2 contents of the injected gas increased the minimum miscibility pressure (MMP) decreased. Displacing agent has a stronger effect in high pressures. It means that partial miscibility supplied by pressure buildup would lead to increasing recovery factor.