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AbstractGas condensate production and gas injection processes are strongly influenced by the gas/oil (or condensate) interfacial tension and by the wetting behavior of oil on the porous substrate. Oil (condensate) recovery is favored by low gas/oil (condensate) interfacial tensions and by complete wetting of oil (condensate) on the water phase that often covers the porous rock. The relevant parameters are dimensionless numbers that measure the importance of the oil/gas interfacial tension relative to gravity (Bond number) and to viscous (capillary number) forces. Another important parameter is the oil/gas contact angle on the water that often covers the porous substrate: a zero contact angle corresponds to complete wetting of oil, while a finite angle corresponds to partial wetting. These parameters are increasingly used in modern reservoir simulators for estimating oil and gas residual saturations and relative permeabilities.We analyze how these parameters vary with the operating conditions (e.g., pressure) and the nature of the injection gas: CH 4 , CO 2 and N 2 . On approach to gas/oil complete miscibility, both the capillary and Bond numbers diverge, i.e., viscous and buoyancy forces dominate over capillary forces. For nearmiscible conditions, these numbers obey simple scaling laws as a function of the distance to complete miscibility. The prefactors of these scaling laws depend on the particular oil+gas system, which allows to classify the efficiency of the different injection gases. For reducing capillary forces with respect to the viscous or buoyancy forces, supercritical CO 2 is more advantageous than off-critical CO 2 or CH 4 , which themselves are more advantageous than N 2 .We also present a simple calculation scheme for predicting the conditions under which the transition to complete wetting of oil on water occurs, i.e., the oil/gas contact angle vanishes.The only ingredients needed are the composition and densities of the three coexisting phases (water, oil and gas), calculated by means of an appropriate equation of state. The essential result is that under typical operating conditions, oils or condensates spread on water, the transition to partial wetting being remote from complete miscibility conditions. CO 2 is the most effective in promoting the wetting (or spreading) of the oil phase on water, followed by CH 4 and then by N 2 .