Abstract: An integrated capacity modelling system for monitoring and controlling multiple oil and gas assets, the system comprising a data acquisition module, capable of acquiring upstream data, whereas upstream data may include information from the multiple oil and gas assets; a subsurface and surface processes simulation module, capable of simulating production and injection performance of multiple oil and gas assets from the reservoir to the sales delivery point; a data assimilation module, capable of extracting key features in the data for the purposes of calculating production capacity of multiple oil and gas assets from the acquired upstream data and from the simulation module and for building an asset capacity model thereof; a data presentation module, capable of presenting all the components of the asset capacity model of multiple oil and gas assets, wherein the presentation module is capable of presenting the asset capacity model of multiple oil and gas assets in nodes of a hierarchical structure of a pluralit