A method, system and apparatus are disclosed for coupling independent reservoir and surface facility network simulators. A reservoir simulator is configured to simulate fluid flow in subterranean reservoirs and a surface facility network simulator is configured to simulate fluid flow in production equipment. Simulation of fluid flow in a subterranean reservoir is initiated using the reservoir simulator. Simulation of fluid flow in production equipment is initiated using the surface facility network simulator. The simulated fluid flow in the production equipment includes fluids produced from the subterranean reservoir. The simulation of fluid flow in the subterranean reservoir is coupled with the simulation of fluid flow in the production equipment using a sub-domain inflow performance relationship.