Generating reliable gas condensate relative permeability data used to develop a correlation with capillary number

The authors have previously reported that steady-state relative permeabilit y measurements conducted using condensing fluids will result in relative pe rmeability increasing with increasing velocity. The techniques used, howeve r, can be experimentally demanding, as individual steady-state points are m easured and the initial condensate saturation in the core is established by condensation. If the data representative of the flow of condensing fluids could be generated using unsteady-stare procedures and conventional gas-oil fluids, as has been suggested in literature, then the duration and cost of the tests would be greatly reduced. To investigate the applicability of co nventional techniques to flow in gas condensate systems, a series of tests were conducted using conventional and condensing fluids. For each set of te sts, the interfacial tension (PT) and flow rate were the same, with the onl y variables being the measurement of steady-state relative permeability whe n using condensing fluids, and the measurement of unsteady-state relative p ermeability when using conventional fluids. The main areas of interest were hysteresis in the relative permeability curves between imbibition and drai nage, and the degree of relative permeability rate sensitivity. It was demo nstrated in this study that conventional methods could produce erroneous re sults when applied to condensing fluids. The steady-state gas condensate ra te sensitive relative permeability data has been used to formulate a new co rrelation that relates gas and condensate relative permeability to capillar y number (the ratio of viscous to capillary forces). The correlation incorp orates two major parts, with exponents and coefficients that appear in the correlation bring determined by regression of the steady state relative per meability data. Comparisons between the measured and predicted relative per meability curves show a good agreement. The study highlights the need to us e condensing fluids when measuring gas condensate relative permeability. (C ) 2000 Elsevier Science B.V. All rights reserved.