1. A method for determining an oilfield parameter for a drilling operation in an oilfield, the oilfield having a well site with a drilling tool advanced into a subterranean formation with geological structures and reservoirs therein, the method comprising: identifying a first set of decision factors about the drilling operation and a second set of decision factors about the drilling operation, wherein each of the first set of decision factors is contained within a first set of nodes, and wherein each of the second set of decision factors is contained within a second set of nodes, wherein both the first set of nodes and the second set of nodes contain a set of common nodes; associating the first set of nodes to create a first belief network and associating the second set of nodes to create a second belief network; associating the set of common nodes of the first belief network with the set of common nodes of the second belief network to form a multinet belief network; and generating at least one oilfield parameter from the multinet belief network.