Experimental investigations of rock-fluid interactions in low salinity water injection for enhanced oil recovery in Shaly carbonate oil reservoirs

Water flooding has regularly been acknowledged as a promising method to maintain reservoir pressure during oil production. The foremost challenge that comes with this approach is the increase in scale potential due to the incompatibility between the injected water and the in-place water due to their diverse physical and chemical properties. In this paper, the thermodynamic conditions for the formation damage caused by the inorganic deposits, swelling of the clay minerals, and their migration through porous media was experimentally investigated, and then the effect of these deposits on the permeability of Shaly-carbonate core samples was investigated. Additionally, the effect of salinity of the injected water on the swelling and non-swelling clay minerals were investigated, and the critical salt concentration (CSC) of the injected water was experimentally and mathematically estimated. The results indicated that the deposition of calcium sulfate ions causes the highest damage factor (up to 60%) with the lowest pore volume (P.V.) of the injected water (7 P.V.), as mostly non-removable damage. Also, the CSC of the injected water reached to the swelling clay inorganics was higher than that for the non-swelling clay minerals. Eventually, the second type of CSCs of the injected waters containing the ions Na+, Na++Ca2+, and Ca2+ were experimentally obtained as 0.5, 0.05, and 0.01 and mathematically estimated as 0.35, 0.06, and 0.01, respectively.