Integrated Asset Modeling (IAM) has now become widely used for oil and gas production optimization. It has the advantage of integrating constraints from reservoir, well inflow and outflow, pipelines, compressors and processing facilities in one integrated simulation model. IAM is also a powerful tool for decision making and planning, it allows a quick and comprehensive assessment of geosciences uncertainties combined with different development strategies. This paper describes how IAM is a key for OML58 gas fields optimization and forecast. It has proven its ability to identify potential benefits of upgrading surface facilities to ensure sustainable gas supply to the Nigeria Liquefied Natural Gas Plant (NLNG) and the domestic market. The OML58 upgrade project comprised the increase of gas compression capacity and the construction of two major pipelines: The Obite-Ubeta-Rumji (OUR) pipeline and the Northern Option Pipeline (NOPL). The commissioning and start-up was completed in August 2016 and the first domestic gas supply to the Alaoji Power Plant was achieved in October 2016, marking an important milestone for Total E&P Nigeria Limited (TEPNG) and its joint venture partner NNPC. The paper also highlights the importance of OML58 IAM in addressing both short and long term challenges. The model is used to maximize condensate production using an algorithm that automatically prioritizes high condensate wells in forecast stage. It also guides the planning and the optimization of well intervention for both data acquisition and production enhancement. In long term perspective, the paper illustrates the flexibility to perform the screening of different infill/workover drilling options, the integration of undeveloped gas fields and the preliminary assessment of gas explorationprospects.