1. A method for enhancing allocation of fluid flow rates among a plurality of wellbores coupled to surface facilities, comprising: modeling fluid flow characteristics of the wellbores and at least one reservoir penetrated thereby; modeling fluid flow characteristics of the surface facilities; in a computer, operating an optimizer to determine an enhanced value of an objective function, the objective function corresponding simultaneously to the modeled fluid flow characteristics of the wellbores and the surface facilities, the objective function relating to at least one production system performance parameter; and allocating fluid flow rates among the plurality of wellbores as determined by operating the optimizer, wherein the at least one production system performance parameter comprises one or more of minimum water production rate and minimum gas/oil ratio.