Unsteady-state model for calculating oil-water relative permeability for reservoirs with low and ultra-low permeability

Key words:  reservoir  low and ultra-low permeability reservoir  unsteady-state  oil-water relative permeability  threshold pressure gradient  capillary pressure  gravity

Abstract:

Based on the characteristics of oil and water flow in porous media, a model for calculating oil-water relative permeability for oil reservoirs with low and ultra-low permeability was developed, in which the effects of threshold pressure gradient, gravity and capillary pressure were considered. A unsteady state method was used to conduct the measurement of the relative permeability, and the relative permeability curves influenced by various factors were then calculated. The results show that the threshold pressure gradient has a prominent effect on the oil-water relative permeability, formation pressure, residual oil saturation, and the recovery of oil production. The gravity also has important effect on the relative permeability and oil production, while the capillary pressure can affect the oil relative permeability, but it has little influence on the water relative permeability.