Conventional carbonated water injection (CWI) induces oil swelling and reduction of oil viscosity and density. The CO2 solubility in carbonated water is a key factor to determine these effects and is sensitive to pressure, temperature, and salinity. The CWI has another aspect of CO2 storage due to solubility trapping mechanism. Low saline water is a favorable condition to solubilize CO2 into brine due to salting-out phenomenon. As well, the low saline water injection (LSWI) has potential to enhance oil recovery originated from wettability modification in a carbonate reservoir. In terms of geochemical aspect, low saline brine introduces higher CO2 solubility and wettability modification effect. It has triggered the evalution of hybrid process, which integrates LSWI with CWI. The CO2 dissolution and wettability modification effects are highly related to geochemical reactions in brine/oil/rock system. This study has constructed the numerical modelling of carbonated low salinity water injection (CLSWI) coupled with geochemical reaction and evaluated the performance in terms of oil production and CO2 storage.

In core and pilot systems, the wettability modification effect of CLSWI contributes to 9% and 15% increased oil recovery over CSWI. In both systems, more CO2 has been captured up to 17% and 45% due to salting-out phenomenon, respectively. CLSWI enhancing oil swelling and oil viscosity reduction has also improved injectivity up to 31% over CSWI in pilot system. The results from this study has demonstrated that CLSWI is a promising water-based hybrid EOR.

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