Over 60 % of the world's daily oil production today comes from giant fields, where production is on decline (Robelius, 2007). Extended development and management of such complex projects would require integrated and cost efficient approach.

While there are many theories on integration of reservoir and network models, there is very limited experience on the actual application of such models to field development plans (FDP) as routine decision making tools. This paper presents successful case study of creating robust and fast integrated model of a giant gas-condensate field with complex gathering network and processing facilities. Use of integrated asset modelling (IAM) approach has proven to bring value over conventional "standalone" modelling in this particular complex system. This system includes three inter-flowing processing facilities simultaneously constrained by processing capacities, gas compression for re-injection and overall export agreements. In addition, all the wells (about 100 producers and 20 injectors) have individual constraints (liquid rate and drawdown limits for producers, injection rate and pressure limits for gas re-injection wells).

Major technical challenges resulting from the complexity of such modelling were discussed here. Increase of stability (honouring all constraints), accuracy (reproducing actual data) and speed (4-5 min per timestep) were achieved by imbedding custom algorithms and workflows into IAM while using fully compositional Eclipse and complex GAP network models. One of the major challenges was to properly model and optimize inter-unit flows and properly prioritize low GOR wells.

In this paper a project from FDP is used as an example to demonstrate the benefits and limitations of integrated modelling approach. Based on the case study example the integrated model has proved to bring incremental value by providing more accurate production profiles and reducing development costs by avoiding "overdesigning". These and other conclusions are discussed in the paper in the context of the actual project.

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