The mechanism of Disproportionate Permeability Reduction (DPR) resulting from polymer or gel adsorption in porous media has been widely reported in the literature in the domain of Darcy regime. However, very few studies have been dedicated to the impact of polymer adsorption in porous media when two-phase flow occurs in non-linear regimes which are of interest in a wide range of applications. The objective of this paper is to report some experimental investigations on the effect of polymer adsorption on gas-water flow at low mean pressure, i.e. when Klinkenberg effects (or gas slippage) must be considered, as well as at high flow rates when inertial effects are significant. The experimental study reported in this paper consists of water and nitrogen injections into various silicon carbide model granular packs having different permeabilities. More specifically, the purpose is to investigate gas flow at different water saturations before and after polymer adsorption over flow regimes ranging from slip flow to inertial flow. In good agreement with previous works, in the Darcy regime, we observe an increase in irreducible water saturation and a strong reduction in the relative permeability to water while the relative permeability to gas is slightly affected. At low mean pressure in the gas phase, the magnitude of Klinkenberg effect is found to increase with water saturation in the absence of polymer, whereas, for the same water saturation, the presence of an adsorbed polymer layer reduces this effect. In the inertial regime, a reduction of inertial effects is observed when gas is injected after polymer adsorption, taking into account water saturation and permeability modifications. Experimental data are discussed according to hypotheses put forth to explain these effects.