For this project, Atmos SIM Online is required to provide a number of different pieces of functionality on the gas pipeline. As the pipeline is subsea, flow, temperature, and pressure metering is only available at the start and end of the pipeline so Atmos SIM is needed to provide calculated data at critical locations within the pipeline, particularly to estimate conditions where condensate can form. Composition tracking is required as gas of different compositions from multiple supplies mixes in the main line. Accurate modeling of the mixing is important for warning of possible condensate formation. There is no composition meter at the demand, so Atmos SIM provides a virtual Composition Measurement at the demand for operations. On top of this SIM was also used to provide the pig tracking for that line. In line with the other applications supplied with this project Atmos SIM was integrated within Atmos SMT to allow the application to be monitored and controlled from the same single interface.

For the liquid lines, no online modeling was required and the stand-alone Atmos Pig was used to provide the pig tracking functionality. The gas pipeline uses the pig tracking functionality within Atmos SIM because velocity varies along the length of the line so an online model is required to give accurate pig velocity, particularly under transient operating conditions.

The trend below is taken from an example Atmos SIM model and shows the velocity and standard flow rate of gas along the length of a pipeline at a given moment in time. From this plot it is clear to see that the velocity of the gas in a pipeline can vary quite considerably even when the flow is steady. To get an accurate pig location under these circumstances an online model is required.

There are a full range of features within Atmos SIM to allow accurate pig tracking on any network. These include; customization of pig properties (e.g. pig length, pre-configured slippage factor, automatic relocation of pigs based on pig signaller instruments or pressure readings, manual relocation of pigs, automatic tuning of slippage factors and tracking of multiple pigs within multiple routes. Information on each tracked pig includes a customizable comment, name, launch time, distance along pipe, distance to end and ETA. Data output from the Atmos SIM pig tracker is identical to the Atmos Pig making both systems fully compatible and able to send calculated outputs and notification alarms to SCADA and DCS via OPC.