Temperature effects on the heavy oil/water relative permeabilities of carbonate rocks

In this study, unsteady-state relative permeability experiments were carried out using unpreserved limestone and dolomite core samples obtained from the oil zones of heavy oil carbonate reservoirs. Experiments were conducted at reservoir pressure and original fluid saturations for a temperature range of 100–500 °F.The oil/water relative permeabilities in various temperatures were determined using the JBN method and history matching of the experimental data using numerical simulations. The applicability and limitations of the JBN techniques are discussed. The results suggest that relative permeabilities of oil and water in heavy oil carbonate systems are functions of temperature. Specifically, the shape of oil relative permeability changes with increasing temperature which might be caused by wettability alterations due to elevated temperature. This, in fact, disagrees with some previous studies dealing with sandstone systems. It was found that the residual oil saturation decreases and irreducible water saturation increases with increasing temperature.