1. A computer-implemented method for updating simulation models of a subterranean reservoir, the method comprising: (a) providing an ensemble of reservoir models representing a subterranean reservoir having non-Gaussian characteristics; (b) providing reservoir data from the subterranean reservoir; (c) solving, for each of the reservoir models in the ensemble of reservoir models, a constrained optimization with equality constraints and inequality constraints to obtain a constrained optimal solution; and (d) assembling the constrained optimal solutions to update the ensemble of reservoir models, the updated ensemble of reservoir models being consistent with the reservoir data provided from the subterranean reservoir and preserving the non-Gaussian characteristics of the subterranean reservoir.