1. A system for modeling an oilfield having at least one process facilities and at least one wellsite operatively connected thereto, each of the at least one wellsite having a wellbore penetrating a subterranean formation for extracting fluid from an underground reservoir therein, comprising: a plurality of wellsite simulators, each of the plurality of wellsite simulators modeling at least a portion of the at least one wellsite of the oilfield; at least one non-wellsite simulator, each of the at least one non-wellsite simulator modeling at least a portion of a non-wellsite region of the oilfield; and at least one coupling positioned among the plurality of wellsite simulators and the at least one non-wellsite simulator, the at least one coupling selectively linking the plurality of wellsite simulators and the at least one non-wellsite simulator according to a pre-defined configuration for selective communication therebetween whereby a model of the oilfield is generated.