This paper addresses the on-line application of ATMOS SIM simulation software, integrated with ABB Network Manager WS500, to a subsea pipeline network of 7,800 km (4,847 mile) length — see Figure 1. The pipeline system is operated by Gassco Norway, and it delivers an annual volume of approximately 100 billion standard cubic meters of Norwegian gas to customers in Western Europe. One of the main challenges to such a great subsea pipeline system is the limited measurements available. For nearly all of the pipelines, the only location where flow, pressure and temperature are measured is at the inlet and outlet which could be more than 800 km (497 mile) apart.

The following applications will be addressed in this paper:

• IT architecture. User controls including Common Alarm List.

• Data validation overview.

• Pipeline inventory calculation.

• Continuous calculation of settle-out-pressures for (sub)sections of pipelines to provide information for emergency shutdown systems.

• Integration of ambient seabed temperatures as provided by UK Met.

• Composition tracking including the possibility to track user specified trace components.

• Estimated arrival times and volumes of “off-specification” gas.

• Tracking of the parentage of batches such that the party responsible for off-spec gas can be identified (polluter pays principle).

• Facilities to restart models from historic data with the possibility to remove erroneous inputs.

• Continuous running of look-ahead cases based on user defined transient time series and nominations for contractual exit points.

• Using larger network models to plan and monitor mixing of gasses to prevent off-spec gas.

Comparisons between simulated and measured values will be made to illustrate the accuracy of the hydraulic models. In addition, the application of Maximum Likelihood State Estimation will be discussed to demonstrate its effectiveness in overcoming measurement errors.

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