Experimental Study of Hot Water Injection into Low-Permeability Carbonate Rocks

Abstract

Hot water drive involves the flow of only two heated phases. The major mechanisms on hot water injection are thermal expansion, viscosity reduction, wettability alteration, and oil/water IFT reduction. In this study, hot water injection experiments were carried out using unpreserved limestone and dolomite core samples obtained from the oil zones of heavy oil low-permeability reservoirs. These experiments were conducted at reservoir pressure but in various temperature ranges up to 500 °F using a wide variety of oils. The final oil recovery, residual oil saturation, irreducible water saturation, and pressure drop were compared in each experiment. The results of dynamic isothermal displacements were interpreted using numerical simulation method to obtain reliable relative permeabilities. Hence, the effects of temperature on oil/water relative permeabilities were obtained for low-permeability carbonate rocks. Results show that it is possible to recover a high percent of oil using high-pressure/high-temperature injection even from heavy oils in low-permeability carbonate reservoirs. In the heavy oil system, the oil production to hot water injection ratio is higher than in the medium and extra heavy oil, but the values are less than the reported values for conventional heavy oil reservoirs. Also, it was found that the relative permeabilities of oil/water depend on temperature and the residual oil saturation decreases and irreducible water saturation increases when the rock is heated.