Design execution, delivery and management of operations of oil and gas facilities involve complex and iterative processes spanning a long period of time from concept to decommissioning. In such complex and large projects, several teams and disciplines participate to the common effort, with their expertise and tools, to provide an overview of the project that is, at the same time, as complete as possible, and manageable. In this process however, teams often work in siloses, with complex and repeated hand over of information and additional effort of coordination. The risk represented by lack of coordination or communication may be severe, especially if not mitigated by sufficient margins. However, as the industry evolves towards improved efficiency, reduction of carbon footprint and, in general, a more sustainable configuration, there is increasing demand of managing uncertainty and complexity, to reduce risks, improve profitability and operate safely. In this work we introduce a novel approach to modelling and simulating the facilities through an Integrated Asset Model (IAM) through a continuous model of the entire asset, from the reservoir to the process. As the project is enriched with details, the model evolves to a real time digital twin, which enables engineers to improve efficiency by breaking down the barriers between disciplines and improving sharing of information and decision-making. In this paper, we show how a more holistic approach to the entire asset can deliver better returns on capital and improve the economics of the entire project. We explore the detail of connecting real time data with rigorous simulation and consistent thermodynamics throughout. This then leads to a single true representation, removing conservative design margins and inconsistencies in operational data; saving your assets time and cost in both the design and operations phases of their lifecycles.