Recent studies on low-salinity waterflooding (LSW) and CO2 water-alternating gas (WAG) use are noteworthy because of their effectiveness in recovered oil content retention in mature fields. s the brine salinity decreases, the solubility of CO2also increases. The CO2in the injected water is expected to reduce the water/oil interfacial tension (IFT), and thus previouslytrapped oil in the rock by capillary forces will flow. However, as of yet, a fewresearches havefocusedon the fluid/fluidinteraction involving waxy crude oil/brinein the LSW-WAGprocess. Twomodels, both of which have been developed from experimental interfacial tension measurements, assist in estimating the CO2's effect on oil/water interfacial tension in the presence and absence of CO2. This objective is accomplished by designing experiments using the modified central composite design (CCD)method in response surface methodology (RSM). Theeffectof pressure, brine salinity, and CO2on oil/water IFT are taken into consideration while modelling.Analysis of variance (ANOVA) was used to determine the optimal values of input variables based on the developed model to obtain an acceptable model. The R-squared values indicate that the developed models arecapable of accurately forecasting the experimental results of oil/water IFT using Dulang crude oil and seven different brine salinities. The findings of this study are expected to shed light on the fluid/fluid interaction behaviour during the LSW-WAG recovery process in a mature field producing waxy crude oil.

Recent research on the combination of low salinity waterflood (LSW) with CO2 water-alternating gas (WAG) has received significant attention due to its effectiveness in recovering residual oil in a mature field. The solubility of CO2 increases with decreasing brine salinity; and the presence of CO2 in the injected water is expected to reduce the water/oil interfacial tension (IFT) leading to the release of trapped oil previously held in the rock by capillary forces. However, to date, little study has been done on the fluid/fluid interaction during the LSW-WAG process involving waxy crude oil and injected brine. In this study, two models have been developed from experimental IFT measurements that can facilitate the prediction of the CO2 effect in the interfacial tension between oil/water interface in the presence and absence of CO2. This objective is achieved by modelling the effect of pressure, brine salinity, and CO2 on oil/water IFT with the response surface methodology (RSM) using the modified central composite design method (CCD) for the experimental design. Based on the developed model, the optimum values of input variables were calculated by analysis of variance (ANOVA) to obtain an acceptable model. The R-squared values demonstrate that the developed models could appropriately predict the experimental results of oil/water IFT from Dulang crude oil and 7 different brine salinity. The results of this study are expected to give insights into the fluid/fluid interaction behaviour during the LSW-WAG recovery process from a mature field with waxy crude oil.

No abstract