Producing oilfields are an excellent target for production re-development plan and optimization projects. All the wells were drilled and producing/injecting, fluid samples and ratios are known, artificial lift methods are usually in place, networks were installed, facilities were dimensioned and historical data is available.This detailed information can be used to feed and calibrate advanced reservoir and network models which can be coupled in an integrate asset modeling platform. Coupling reservoir simulation models with surface networks permits each discipline, reservoir and production, to focus on detailed representation of field information gathered and allows the constrains of each part of the system to be imposed simultaneously.Therefore, integrated asset modeling generates representative field production forecast and the opportunity to quantify many improvement scenarios options. These options are not limited but include modify gas-lift allocations, surface back-pressures and increase facilities capabilities.This paper describes the methodology applied to the development of an integrated asset modeling study for a brown offshore oilfield in Brazil and the technical challenges faced. The project conducted included six reservoir models coupled to oil production, water injection and gas-lift distribution networks in order to evaluate the current production and future optimization scenarios.The results obtained with this project demonstrated the impact of current water treatment facility in the field oil recovery and the potential gains associated with gas-lift optimization. ReservoirThis Integrated Asset Model study was performed on a field that contains some reservoir compartments, each of them modelled with one independent reservoir model using ECLIPSE. The field layout consists of one single production platform with production fluid limit of 180,000bbl/d and water treatment maximum capacity of 100,000bbl/d. Producing Network ModelThis Integrated Asset Model project includes wells, production network and facilities, gas-lift delivery network and water injection system. The entire network was developed using PIPESIM software for well and network modeling. All producing wells are satellite with a dedicated flowline and riser to connect each well to the production platform.This project was developed using stages approach so that the huge amount of data and modeling work involved could be managed efficiently and smoothly. The major stages were: