We present a comprehensive numerical method to calculate well impairment based on steady-state radial flow. It incorporates near-critical relative permeability and saturation dependent inertial resistance.

Example calculations show that near-critical relative permeability and non-Darcy flow are strongly coupled: Inertial resistance gives rise to a higher capillary number, which makes the use of proper near-critical relative permeability curves all the more important. In its turn, the improved mobility of the gas phase due to a higher capillary number enhances the importance of the inertial resistance.

The combined effect of condensate drop-out and non-Darcy flow may cause large skins in gas condensate reservoirs. Well impairment may be grossly overestimated if the dependence of relative permeability on the capillary number is ignored.

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