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Abstract Management of field development, and determining optimum operating plan requires reliable information on the pressure and rate behavior of the formation as well as on the performance, stability and deliverability of the surface & production network. The integration of the network simulator and optimizer. NETOPT with the reservoir simulator. ECLIPSE uses a robust convergence procedure in an interface that tightly couples the two simulators. The integrated solution becomes an effective tool for field development and management. Introduction Field-wide planning over the life of a reservoir has been the subject of considerable interest in recent years. The ability to rigorously incorporate the effect of surface multiphase piping networks, as well as changing compression, separation and pumping facilities is critical for the accurate simulation of reservoir behavior for planning purposes. The development of an interface that integrates a production & surface network simulator with a reservoir simulator is the initial step in creating a field-wide planning tool. In the integrated solution, the network simulator determines the behavior of production or injection wells in the wellbore and through surface facilities while accounting for reservoir behavior over time. The reservoir simulator characterizes the fluid flow, saturation and pressure behavior within the formation, and determines the inflow performance (IPR) for each well at its grid block. An equivalent IPR is also incorporated in the network simulator. Individual well controls are implemented on the network side, however additional controls such as a drilling schedule may be imposed by the reservoir model. The network simulator honors production allocations or group controls that currently reside in the reservoir model. Integrated Simulation Approach The two programs are integrated using Parallel Virtual Machine (PVM) interface, eliminating any necessity for file exchange. The network simulator acts as the master program sending and receiving messages that include flow rates and pressures for each well in the integrated simulation model. Reservoir simulator provides local inflow performance data as a function of flow rate, sandface pressure and cell block pressure within the time step, which determine the boundary conditions to simulate the production systems & surface facility performance. Simulation advances a time step after rate & pressure convergence is achieved within the predetermined tolerance. Field Study In this field application, the reservoir simulator has a 20x15x8 grid with 1639 active cells. A total of 19 wells are included in this grid (Fig. 1). 8 wells are water injectors. 1 well is a gas injector, and 10 wells are producers. All producers are included in the network simulation; injectors are not tied into a surface network however they do affect the production network since performance of the producers are tied to the overall flow and pressure behavior within the reservoir. The wells are on a drilling schedule. Initially, there is only one well flowing. The remaining wells come into production in 2 to 6 month intervals. Two of the wells, LU1 and LU2 which are the first two to be producing, have a maximum water-cut limit of 70%. In addition, wells can be shut in by the reservoir simulator due to economic limits. The simulation runs to 1720 days (4.7 years) under surface network control. There are no chokes or other flow constraining devices in production network. (Fig. 2).