Optimizations of oil productions in current practices have been done separately in both subsurface and surface facilities. This approach might not lead to an optimum state when the whole system is interconnected. In this work, a superstructure model of an existing integrated subsurface and surface facilities was developed and evaluated to maximize the oil productions. In subsurface facilities, well performance data were taken from PROSPER well simulations. Operating variables such as downstream pressures of choke valves and gas lift flowrates, which influence the flow of oil, gas, and water from reservoirs, were considered. Based on these variables, performance correlations of the wells were then developed. On the evaluated surface facility, three pressure levels of vessels on the platform (high-, medium-, and low-pressure vessels) and their current designs were also considered. The optimization result shows that to reach optimum oil production, one well should be connected to the high-pressure vessel, four wells to the medium-pressure vessel, and the rest goes to the low-pressure vessel. Several choke valves and gas lift flowrates also need to be adjusted accordingly. © 2019, The Author(s).