ABSTRACT
A determination of oil relative permeability data during secondary and tertiary, gravity stable, nitrogen injection experiments is described. Four experiments were conducted at high and low pressure using vertical Clashach sandstone cores and a dead oil in the presence of connate brine. The spatial distributions of oil throughout the cores were determined using a radioactive tracer technique and these in-situ saturation measurements were used to determine the oil relative permeability.
The results of two new experiments are presented. A high pressure, secondary, gravity stable, nitrogen injection was conducted in a 1790 mm core with a connate water saturation of 0.25. The residual oil saturation following 12 days of gas flooding was 0.19. A low pressure, tertiary, gravity stable, nitrogen injection was conducted in a 841 mm core with a connate water saturation of 0.19. A residual oil saturation to water flooding of 0.51 was reduced to 0.09 after 37 days of drainage.
The rate of change of oil relative permeabilities with respect to oil saturation was larger in the secondary, gravity stable, nitrogen injection than in the tertiary injection. The predicted residual oil saturation to gas corresponding to an infinite drainage time appears to be finite for secondary gas injection and zero for tertiary gas injection.
The permeability data is consistent with a theoretical model of film drainage which predicts a Corey Exponent of three.
