AN ENGINEERING APPROACH TO MEASURING AND MODELING GAS CONDENSATE RELATIVE PERMEABILITIES

摘要

An experimental procedure for measuring relative permeabilities in the near-well region of a gas condensate well has been developed.A high-pressure/high-temperature closed-loop apparatus was designed and built.The system includes in-line PVT measurements of oil relative volume and oil viscosity.One major advantage of performing the relative permeability measurements in a closed-loop apparatus is the ability to flood large volumes of gas and condensate through the core,securing steady-state equilibrium at each step.Special hysteresis effects were studied,including velocity and drainage/imbibition hysteresis.Significant hysteresis effects were not observed for the two core experiments performed on a Berea and a North Sea sandstone.The hysteresis experiments were performed using two different synthetic gas condensate fluid systems.Relative permeability measurements have been performed using both synthetic and reservoir gas condensate fluid systems.Similar results were obtained for the three fluid systems,with no significant effect of fluid system observed.Gas-oil interfacial tension(IFT)effect on relative permeability was studied by varying the core pressure.The velocity effect was studied by varying injection rates.IFT/velocity studies were performed on two Berea cores using synthetic and reservoir gas condensate fluid systems,and using one reservoir core plug with a synthetic gas condensate fluid system.Consistent results were obtained for the experiments.The key relation to define in steady-state flow tests of gas condensates is k_(rg)as a function of k_(rg)/k_(ro).Strictly speaking,saturations are not necessary to measure.Once the krg=f(k_(rg)/kro)relationship is experimentally established and correlated with capillary number(Nc),relative permeability curves can be modeled.A program for fitting steady-state gas condensate relative permeability data has been developed and used for modeling relative permeability curves.