Fluid Tracking is an inherent component of the simulator model. It is essential if the fluid from one or more sources is variable or different to other sources and the fluid is later mixed at pipeline junctions. The fluid property variation is tracked throughout the pipeline / network, mixed at pipeline junctions and used to calculate accurate, flow, pressure and temperature profiles.
VariSim tracks all fluid variations with product interfaces launched through a number of mechanisms. It tracks the position of the changes in fluid property variance based upon the locally calculated velocity. Product advancement is not just calculated on the amount of volume that has entered the pipeline, product compression / expansion is fully taken into account.
As standard, each packet holds the following information:
Fluid type (for liquids) or composition (for gases)
The volume of the packet at standard conditions
The location of the downstream interface of the packet
The base properties of the packet contents including density, viscosity and thermal data
The age of the product (how long the product has existed in the pipeline)
Physical Tracking includes the tracking of any physical component of the system not directly related to the fluid. This includes pigs / scrapers, chemical dosages or inhibitors, drag reducing agents (DRA) and batch separators.
The pig-tracking module continually tracks the progress of a pig that has been inserted into a pipeline section. It then accurately calculates the expected time of arrival at any pre-defined location on the pipeline section based on the product velocity, the characteristics of the pig and the pig slippage factors. Pig slippage factors are calculated and updated with each successive pig run.
DRA tracking tracks the concentration of DRA from its injection point and determines its effectiveness based upon distance travelled, time, pipeline turbulence and the type of equipment through which it passes. The effectiveness of the DRA is linked to the simulation model to reflect the effect of the DRA on the pipeline hydraulics.
Virtual Tracking is the tracking of any non-physical ‘virtual’ component of a product and includes:
Batch management information
Quality indicators (e.g. wobbe values and ICF for gas pipelines)
Ownership (indicating the source of the product and the ratio of product from this source to other sources)
Injection volumes needed (e.g. N2 injection requirements)
Operator marked products, any component of the product can be displayed (such as a marked low quality Crude or high H2S content etc.)
The pipeline efficiency function monitors the deterioration in the pipelines condition. This may occur as a result of pipe wall deterioration, detritus build up, waxing, hydrate formation etc. Efficiency alarms can be raised to signify the need to pig the pipeline
The maintenance scheduler monitors the instrumentation installed on the pipeline / network. In its simplest form, it provides clear output to the operator advising of the date that instrumentation was last maintained. It raises events for the operator advising of the next scheduled maintenance date and alarms if the due date expires. It is entirely configurable by the operator and can be updated as and when required.
In its more advanced form, the instrumentation can be monitored for drift by comparing its calculated output against other instrumentation data or calculated data provided by VariSim. This feature links with the historian process to allow detailed performance analysis over extended time periods. It makes use of the powerful data assessment tools for identifying long term drifting, drop outs and ‘jumps ‘ in measurement. The instrument analysis process helps improve the quality of the measured data that is presented to an operator and has the unique advantage of being able to use simulated data from VariSim in its analysis process. This not only improves the reliability of the SCADA data that the operator uses in the day to day decision making process, it also serves to identify anomalies in the behaviour of a pipelines operation and improves the accuracy of VariSim simulator. This in turn improves the accuracy of the applications that surround VariSim such as leak detection.