Geochemical modelling of acid injection in high salinity sandstones at reservoir conditions

Waterflooding is widely implemented to enhance oil recovery. The displacement efficiency of this method depends on multiple factors, including makeup water properties, native oil, and formation rock. The incompatibility of the injected fluid with the pore fluid can result in a chemical non-equilibrium state within porous media that may result in different chemical reactions that depend on the type and number of the existing components within the system. The present research aims to develop a mathematical model capable of handling multiple geochemical reactions to predict pH and ions concentration during an acid injection while considering alterations of rock and fluid properties. The dependency of fluid properties (viscosity and density) is considered based on the system ionic concentration, which can be more crucial in high saline media. The validity of the developed model was evaluated using the experimental literature data. The results reveal that in addition to the effect of injected fluid pH, the process efficiency can be influenced by the composition of the injected fluid. In other words, fluid properties dependency on salinity and the injected fluid composition is significant during geochemical simulations. Comparing homogenous and heterogenous mineral distribution shows an insignificant sensitivity to the amount heterogeneity while the total mineral contents remain constant in both cases.