  Carbonated water flooding (CWI) increases oil production due to favorable
dissolution effects and viscosity reduction. Accurate modeling of CWI
performance requires a simulator with the ability to capture the true physics
of such process. In this study, compositional modeling coupled with surface
complexation modeling (SCM) are done, allowing a unified study of the influence
in oil recovery of reduction of salt concentration in water. The compositional
model consists of the conservation equations of total carbon, hydrogen, oxygen,
chloride and decane. The coefficients of such equations are obtained from the
equilibrium partition of chemical species that are soluble both in oleic and
the aqueous phases. SCM is done by using the PHREEQC program, which determines
concentration of the master species. Estimation of the wettability as a
function of the Total Bound Product (TBP) that takes into account the
concentration of the complexes in the aqueous, oleic phases and in the rock
walls is performed. We solve analytically and numerically these equations in
$1-$D in order to elucidate the effects of the injection of low salinity
carbonated water into a reservoir containing oil equilibrated with high
salinity carbonated water.
