Advancing CO2 Gas/oil Injection at Different IFT Assessment in Carbonated Reservoir through Innovated Gas Injection Design

Abstract The injection of miscible/near-miscible gases as a displacing fluid is a commonly used process among the various EOR methods. Nevertheless, despite the difficulties in distinguishing between the actual conditions of miscibility (miscible, near miscible and immiscible), there is substantial doubt surrounding the actual conditions of the displacement process. Gas/oil IFT is regarded as one of the most critical fluid characteristic properties in oil reservoirs affecting gas injection production. As IFT does not appear in the flow equations directly, it is difficult for the current commercial reservoir simulators to capture its effect. Very few experimental data are available in the literature on displacement involving low IFT. However, those data that are available were based on synthetic rather than crude oil. Hence, for better gas flood performance predictions, reliable experimental data must be measured at different IFTs at different levels under reservoir conditions. In this part of the study, a series of two-phase CO2 gas/oil core flood experiments was performed under reservoir conditions in a carbonate core. The objectives of this study were, firstly, to investigate the performance of gas injections under different CO2 gas/oil IFT levels, known as immiscible (5.75mN.m−1), intermediate miscible (0.12mN.m−1), near miscible (0.043mN.m−1) and miscible. Knowledge of these effects is critical for the accurate prediction of the performance of different types of gas injection. The second objective was to utilise unsteady state core flood data at different IFTs to obtain a reliable gas-relative permeability for CO2 gas flooding. The performance of miscible and near-miscible CO2 gas in terms of oil recovery was investigated and compared. This study addresses the problem of developing a new strategy for predicting reservoir performance when applying continuous CO2 flooding.