This work presents a methodology to evaluate the economic attractiveness of installing technologies for oil-water (O-W) subsea separation and produced water re-injection (PWRI) in offshore fields, using Integrated Asset Modeling (IAM).The proposed methodology was tested in the benchmark case UNISIM-I-D.Submodels of reservoir, wells, production network and economic modeling were explicitly coupled and used to obtain production forecasts and to perform economic evaluations including the subsea technologies.The equipment modeling includes a subsea O-W separator located at the producer wellhead and a subsea pump, which directly re-injects the separated water into the injector wellhead.Although simplified, the model allowed the assessment of the implementation from a reservoir engineering perspective.The installation of these technologies benefits the environment because the produced water from the wells is used for re-injection, reducing discharge to the sea.Separating water from the hydrocarbon stream aims to improve the oil recovery factor (ORF), relieving the water-and-liquid capacity of the platform, anticipating oil production (associated with high amounts of produced water), and consequently, increasing the value of the project.Quantifying the value of these new technologies is a complex task because of the uncertainties and risks involved in installation and operation.The economic assessment of the implementation was performed using the value of technology (VoT), which estimates its incremental benefits, showing significant improvements in the cases tested.This interdisciplinary work combines areas of reservoir engineering, production engineering and economic calculations to build a coupled model.This model is then used to analyze production scenarios and production network configurations, calculate the economic potential of subsea technologies for field development, and support decision-making during field management.