1. A method of developing a petroleum reservoir according to a development scheme defined from a computer implemented representation of the reservoir, the representation comprising a grid associated with maps of properties of the reservoir, each map being a realization of an identical random function defined from static data and obtained by a stochastic simulation, wherein dynamic data are acquired during development of the reservoir, and the maps are modified to minimize a difference between the dynamic data and dynamic data simulated by the representation of the reservoir and a flow simulator, comprising: selecting a perturbation method utilizing perturbation parameters for perturbing the maps without modifying the coherence of the perturbed maps with the static data; modifying the parameters by applying a method using a Ensemble Kalman Filter to the perturbation parameters and to the simulated dynamic data; modifying the maps by using the perturbation method with the modified parameters with the perturbed maps verifying the spatial variability model deduced from the static data; adjusting the reservoir development scheme by accounting for the modified maps; and developing the reservoir using the modified development scheme.