Gas- oil relative permeability at near miscible conditions: An experimental and modeling approach

Reliable relative permeability curves of oil–gas systems are important for successful simulation and modeling of gas injection, especially when the miscibility condition approaches. In this work, the relative permeability of a CO2-light oil system has been measured under different conditions, using the Civan and Donaldson (1989) method. Dolomite and sandstone core samples were used in the experiments. The minimum miscibility pressure was calculated using an empirical correlation, as well as slim-tube simulation. Due to some controversial assumptions of the Civan and Donaldson method, such as immiscible and incompressible displacement, history matching was used for predicting the reliable relative permeability of each phase at near miscible conditions. The Civan and Donaldson method was used to predict the relative permeabilities as the initial guesses for the history matching. We found that the Civan and Donaldson method underestimates oil relative permeability. Moreover, the effect of near miscibility on the gas phase relative permeability curve was stronger and the intersection point of the oil and gas phase relative permeability curves occurred at lower gas phase saturations. The results are helpful for understanding near miscible relative permeability behavior and provide knowledge on fluid flow at low IFT conditions during gas injection projects.