This paper analyzes the effects of geological heterogeneity representation in a producing reservoir, when different stochastic simulation methods are used, so as to assess the consequent effects on flow responses for different Enhanced Oil Recovery (EOR) techniques employed. First, the spatial heterogeneity of a fluvial reservoir is simulated using three different stochastic methods: 1) the well-known two-point sequential Gaussian simulation (SGS), 2) a multiple-point filter-based algorithm (FILTERSIM), and 3) a new alternative high-order simulation method that uses high-order spatial statistics (HOSIM). Numerical results show that SGS suffers from the inability of describing the highly permeable channel network whereas FILTERSIM better reproduces this connectivity. By means of the recent HOSIM, a more appropriate description of the curvilinear high-permeability channels is obtained. Second, the realizations generated above represent permeability fields in EOR numerical simulations. In particular, four different methods are considered, namely: 1) surfactant, 2) polymer, 3) alkaline-surfactant-polymer and 4) foam flooding processes. The numerical results show that properly reproducing the main geological features of the reference images has a higher impact if surfactant or alkaline chemicals are injected rather than polymer or foam. This is due to the fact that these latter chemicals act by mitigating the effects of heterogeneities.