Carbonate rocks account for more than half the world's hydrocarbon proven reserves. Oil recovery from these reservoirs is a challenge due to their complex nature. Several enhanced oil recovery techniques have been proposed for improving the oil recovery from carbonate reservoirs. One of the emerging improved oil recovery (IOR) techniques for wettability alteration in carbonate reservoirs is low salinity water injection (LSWI). The popularity of this technique is because of the simplicity of the process compared to other EOR processes. Another commonly used and favorable EOR technique especially when a gas source is available along with high API crude oil and low permeability formations as in carbonates is Carbon Dioxide (CO2) injection. Several studies have been conducted on LSWI at laboratory-scale and to a limited extent at field-scale. Most studies have confirmed a positive response to low salinity injection, which is translated into additional oil recovery in both secondary and tertiary injection modes. Wettability alteration is believed to be the main mechanism underlying additional oil recovery due to LSWI; however, some other mechanisms were suggested such as dissolution processes.
Few LSWI modeling studies have been performed so far especially on carbonate rocks compared to sandstone rocks. Some of the reasons for this reluctance are the lack of clay, the complex chemical interactions between COBR, the heterogeneity of carbonate rocks, and the discrepancy in some of the published results in the literature. Therefore, we propose a LSWI model for oil recovery prediction using the UTCHEM simulator and even move a step further by modeling the effect of combining CO2 and LSWI on oil recovery using the UTCOMP simulator. The modeling work is conducted by shifting the relative permeability curves and altering the residual oil saturation.