The contemporary energy transition will be characterized by many sub-transitions in the next three decades. Oil and gas will continue to play a very important role coupled with renewable energy sources in an energy mix scenario. In this context, the authors of the present work developed a project, named RELife (Renewable Energy for a new Life of offshore platforms), with the main goal of develop a model for the reuse of offshore Oil & Gas platforms at end-of-life stage for the production of renewable energy. In this paper, by considering two types of platforms (4-legged platform with 3 or 4 production wells), various technical scenarios are studied and investigated and for each scenario also the environmental and economic feasibility is evaluated. In addition, all the sub-models are compared with a standard decommissioning process. The evaluations are made for both the Adriatic Sea and the North Sea, two geographic areas with different availabilities of renewable resources. In order to assess also the economic and environmental feasibility, a Discount Cash Flow Analysis and a Life Cycle Assessment of all the scenarios have been conducted.