Chemical Compositions in Modified Salinity Waterflooding of Calcium Carbonate Reservoirs: Experiment

Abstract Modified or low-salinity waterflooding of carbonate oil reservoirs is considerable economic interest because potentially inexpensive incremental production. The injected modified brine changes the surface chemistry rock and crude interfaces detaches some adhered oil. Composition design to enhance recovery determined by labor-intensive trial-and-error laboratory corefloods. Unfortunately, limestone, which predominantly consists aqueous-reactive calcium carbonate, alters composition mineral dissolution/precipitation. Accordingly, reactivity hinders rational brines tailored improve recovery. Previously, we presented a theoretical analysis 1D, single-phase injection into carbonate-rock that accounts for dissolution, ion exchange, dispersion (Yutkin et al. in SPE J 23(01):084–101, 2018. 10.2118/182829-PA ). Here, present results waterflood-brine experiments verify framework. We show concentration histories eluted from Indiana limestone cores possess features characteristic fast 2:1 high dispersion. reaches chemical equilibrium inside porous even at rates higher than 3.5 $$\times$$ × 10 $$^{-3}$$ - 3 m s $$^{-1}$$ 1 (1000 ft/day). Ion exchange salinity waves observed experimentally, while responsible long history tails. Using verified framework, briefly explore how these processes modify aqueous-phase during designer calcium-carbonate reservoir. Because initial brines, affects concentrations only area carbonates/limestones, such as chalks. Calcium-carbonate dissolution aqueous solution pH. affected all processes.