Abstract: Method for enhancing oil recovery in a hydrocarbon-containing carbonate reservoir including: injecting a slug of an oil recovery solution into the carbonate reservoir such that the wettability of a rock surface of the hydrocarbon-containing reservoir is altered toward more water-wet; and injecting a slug of a displacing fluid into the hydrocarbon-containing carbonate reservoir formation after injecting the slug of the oil recovery solution. The oil recovery solution comprising: a manganese-bearing aqueous solution having manganese ions and one or more major ions. The aqueous saline solution having a concentration of manganese ions between 100 and 1,000 ppm TDS and a concentration of major ions that is equivalent to the concentration of major ions in seawater as it is found in nature. The one or more major ions can include: sodium ion, magnesium ion, calcium ion, chlorine ion, sulfate ion, bicarbonate ion, and combinations of the same.

Abstract: Method for enhancing oil recovery in a hydrocarbon-containing carbonate reservoir including: injecting a slug of an oil recovery solution into the carbonate reservoir such that the wettability of a rock surface of the hydrocarbon-containing reservoir is altered toward more water-wet; and injecting a slug of a displacing fluid into the hydrocarbon-containing carbonate reservoir formation after injecting the slug of the oil recovery solution. The oil recovery solution comprising: a manganese-bearing aqueous solution having manganese ions and one or more major ions. The aqueous saline solution having a concentration of manganese ions between 100 and 1,000 ppm TDS and a concentration of major ions that is equivalent to the concentration of major ions in seawater as it is found in nature. The one or more major ions can include: sodium ion, magnesium ion, calcium ion, chlorine ion, sulfate ion, bicarbonate ion, and combinations of the same.