An Experimental Investigation of the Effect of Pressure Gradient on Gas-oil Relative Permeability in Iranian Carbonate Rocks

The authors examine the effect of pressure gradient on gas-oil relative permeability in horizontal and vertical immiscible displacement. The experiments are conducted on a core from lower Dalan formation in the South Pars oilfield of Iran, in constant pressure, unsteady-state condition, and different pressure gradients. The Toth method is used for calculating the relative permeability and plotting proper curves. Data analysis and the effect of pressure gradient on gas-oil relative permeability are investigated. Results show that relative permeability curves are affected by pressure gradient and this effect is much prominent at low pressures due to end-effect phenomena. The dependence of relative permeability curves on pressure gradient is correlated as a function of dimensionless capillary number The accuracy of this correlation for relative permeability prediction is examined and a new method is introduced to minimize the end-effect phenomena on relative permeability curves.