ABSTRACT

Enbridge Pipelines Inc has implemented computational pipeline monitoring (CPM) systems to provide an additional method of leak detection on all 16 of their liquid hydrocarbon pipelines. These pipelines are located both in Canada and the United States where periodic testing of the CPM systems to determine their continuing effectiveness is mandated. Enbridge Pipelines Inc is developing a SCADA interfaced, transient simulation based, CPM test system to comply with this regulatory requirement. In Canada, the National Energy Board, through the reference of CSA Z662 Appendix E, requires that "the leak detection system shall be tested annually to demonstrate its continued effectiveness". In the United States, the Federal Regulation Title 49, Volume 3, Part 195, through the reference of API 1130, requires that "CPM applications should be tested on a 5 year interval". The Enbridge Pipelines Inc Material Balance System (MBS) is a real-time transient model based CPM system. The effectiveness of the MBS on one of the pipelines is verified yearly by fluid withdrawal testing. The effectiveness of the MBS on another pipeline was verified once by fluid withdrawal testing. While fluid withdrawal testing may be the definitive form of testing, cost, complexity, geographical limitations, and the possibility of an accidental product release limit the applicability of this method. The use of API 1149 calculations to determine the maximum theoretical leak detectability (or minimum threshold) is detailed in the paper. The use of simulated fluid withdrawals in a SCADA interfaced trainer environment to test the leak detection capabilities of the MBS implementations and the verification of these tests with actual fluid withdrawal tests is discussed.

1. Background

Computational Pipeline Monitoring (CPM) systems (also called software based leak detection systems) use pipeline data to infer leaks on the pipeline and/or to alarm upon hydraulic anomalies that have the characteristics of a leak. These systems are in place to alert the Pipeline Controller so he/she can evaluate the cause and as necessary to shutdown the pipeline and minimize the size of a spill. In the operation of hydrocarbon liquid pipelines, CPM systems are either mandated by legislation (e.g. in Canada) or must meet regulatory requirements when they are installed (e.g. the current situation in the United States). In the United States (US) the requirements for CPM systems are outlined in CFR 49 Part 195 section 195.444 and these in turn reference the American Pipeline Associations publication API 1130 "Computational Pipeline Monitoring. In Canada, the regulations are in The National Energy Board's Onshore Pipeline Regulations and those reference the Canadian Standards Association Z662 Oil and Gas Pipeline Systems standard and its Appendix E "Recommended Practice for Leak Detection Systems". Enbridge has implemented CPM systems on almost all of its pipelines and have named the systems Material Balance Systems (MBS). All individual pipeline MBS are standardized to one software application, the AdvanticaStoner Leakfinder which is a real time transient model. The software is customized to each pipeline by Enbridge SCADA staff.

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