This invention relates to a method comprising a determination of a first group of facies as a function of the local values of proportion of the groups of facies for each mesh cell of the model. If said first group is among the first set of groups, the neighboring mesh cells are the current virgin mesh cells neighboring the set of connected mesh cells, otherwise they are the current virgin mesh cells neighboring mesh cells associated with a group. A second group is determined for each neighboring mesh cell as a function of the local values of proportion of the groups of facies for said current virgin mesh cell and if the second determined group of facies corresponds to the first group of facies, identification of said current virgin mesh cell as a candidate mesh cell.