Relative permeabilities at near-miscible conditions: effects of connate water saturation, wettability, hysteresis and permeability

We present a series of two-phase (oil and gas) drainage and imbibition relative permeability (kr) curves at near-miscible (IFT=0.04 mN/m) conditions. An equilibrium mixture of methane/n-Butane at 38°C and 1840 psia was used as the oil and gas in the unsteady-state coreflood experiments which were carried out to obtain the kr curves. A high-permeability (1000 mD) and a lower permeability (65 mD) cores were used in the experiments and both water-wet and mixed-wet wettability conditions were examined. The results show that the present of immobile water saturation in water-wet cores could improve oil relative permeabilities and reduce gas relative permeabilities in both imbibition and drainage directions. The results show that despite a very low gas-oil IFT, there is still significant hysteresis between imbibition and drainage cycles for both the oil and gas relative permeabilities in the 65md core. The results help us better understand the impacts of some of the important parameters of multiphase flow through porous media on kr curves and their hysteresis especially in low IFT gas-oil systems and mixed-wet rocks. Obtaining accurate kr and kr hysteresis is extremely important for predicting the performance of gas injection in oil reservoirs.