1. A method for scaling data of a reservoir model, the method comprising: defining a set of models using a computer, each model in the set including meshes with given dimensions, the meshes each including cells; receiving statistical data relative to porosity and permeability using the computer, the statistical data including laws of porosity and permeability distributions and a variogram defined by correlation lengths L H , L V along two distinct directions H, V, the laws and the variogram being applicable to each model in the set; assigning, using the computer, cell permeability values k Hi and cell porosity values Φ Hi depending on the statistical data; scaling, using the computer, a mesh permeability value K H for each of the meshes, based on a mean power formula K H ω H ∝ ∑ k H i ω H relating the mesh permeability value K H to the cell permeability values k Hi of the cells via a power coefficient ω H of having a relationship ω H = Arctan ⁢ ⁢ α π - Arctan ⁢ ⁢ α , the power coefficient ω H being analytically modified to correct a non-ergodicity bias due to the given dimensions of a relevant mesh by a non-ergodicity parameter depending on mesh dimensions D H , D V , according to the relationship ω H = Arctan ⁢ ⁢ α π - Arctan ⁢ ⁢ α , wherein α = L H L V × k V k H ⁢ ɛ and k V k H ⁢ ⁢ and ⁢ ⁢ L H L V designate petrophysical and geostatistical anisotropies of each model in the set, respectively, the anisotropies depending on the statistical data; and determining, using the computer, reservoir permeability and porosity values based on the set of models, using the scaled mesh permeability values.