1. A method for estimating variability of future recovery of a natural resource, the method comprising: receiving, from a database, a plurality of model realizations of the natural resource, the plurality of model realizations representing uncertainty in determining model properties of the natural resource; determining, for each of the plurality of model realizations, respective principal flow pattern coefficients representing a reduced model space; identifying similar principal flow patterns amongst the received plurality of model realizations using the coefficients representing the reduced model space; clustering the received plurality of model realizations according to the identified similar principal flow patterns in the reduced model space, each cluster having a similar principal flow pattern and representing a prior input to a computationally intensive history matching process; and determining variability in natural resource production by future recovery scenarios represented by one or more representatives of each of the clusters of the received plurality of model realizations, wherein the determining the variability comprises a subsequent history matching process and a consequent future simulation to estimate the future production scenarios of the natural resource; wherein a processor connected to a memory device is configured to perform: the receiving the plurality of model realizations, the determining the respective principal flow pattern coefficients, the identifying similar principal flow patterns, the clustering the received plurality of model realizations and the determining the variability.