Development of marginal deep water fields requires an integrated and cost-effective approach for costs minimization and production enhancement by synergies with existing surrounding infrastructures. This paper details the successful use of Integrated Reservoir and Production Modelling to unlock the development of three marginal deep water oil discoveries in synergy with an existing surrounding subsea development. A marginal field is usually defined as a field that may not produce enough net income to make it worth developing. Deep water satellites are among those, requiring important development optimizations to unlock their potential. Integrated Reservoir and Production Modelling is largely used within the Oil and Gas industry for evaluating production forecasts associated to development assumptions by modeling the fluid flow from pore to process while honoring all required subsurface to surface constraints. This paper describes how the use of such modeling approach has been used to unlock the development of these marginal oil discoveries by evaluating the value of different development concepts from stand-alone to tie-back together with standardized and under-qualification subsea technologies. The Integrated Reservoir and Production Models were made of the three reservoir dynamic models of the three marginal fields connected to the well and network production models capturing the various concepts evaluated. Three main development concepts have been tested: stand-alone, short tie-back to field X and long tie-back to field Y. For all these concepts, many sensitivities have been performed: well implementation patterns, well completion and activation, production and injection networks design including subsea boosting and surface capacities debottlenecking. Tie-back to field X has then been further evaluated to determine detailed bases of design maximizing the value of the project. Integrated Reservoir and Production Modelling has been key to enable cross-functional team work and determine the best incremental value of these marginal fields in synergy with the production of the surrounding existing field.