ABSTRACT

Pipeline modeling in a real-time, on-line environment enables pipeline operators to better analyze and understand the physical characteristics of their facilities and consequently to operate their pipeline more efficiently and economically. The purpose of a real-time pipeline model is to provide an accurate representation of current and future pipeline operation. To verify the continuous accuracy of the real-time and predictive models, calculated results are compared to SCADA measurements. Confidence in the models capabilities is achieved only when the different application models yield accurate results operating under various real-time transient conditions. This was accomplished with extensive testing prior to and during the Site Acceptance Test (SAT) phase. LICconsult, Inc. (LIC) has recently implemented an on-line real-time pipeline simulation software system for Northern Border Pipeline Company (NBPL), a US based pipeline operated mainly from Houston, Texas, with a backup system in Omaha, Nebraska. This paper was prepared to provide some insight into the extensive testing performed prior to and during SAT on the pipeline simulation software system. Moreover, this paper describes actual test cases and identifies the benefits realized through the successful implementation of modeling techniques.

MODEL CONFIGURING AND TESTING

The NBPL pipeline system is located in the northern part of the United States, traversing Montana, North Dakota, South Dakota, Minnesota, and terminating in Iowa. Daily firm capacity of this 970 mile system is 1.675 billion cubic feet. A total of 7 compressor stations are located along the transportation routes. The average distance between the existing compressor stations is 120 miles. An effective real-time model must accurately simulate the physical details of the pipeline system and the operational characteristics of the compressor units. To prepare for the implementation of the real-time model, extensive pipeline data was accumulated and integrated into the model database. Detailed compressor performance curves incorporating head, flow, speed, horsepower, fuel consumption, efficiency, surge and choke equations are also an integral part of the software model. An accurate calculated representation of the current state of the pipeline is necessary to simulate future operational changes and to yield meaningful results. Once the pipeline is configured and the pipeline simulation software is installed, the results are evaluated by comparing the model results to SCADA measurements under various transient conditions. This paper will not cover pipeline configuration details or the various model applications. It will however summarize some of the tests that focused on modeling compressor stations. The main purpose of these tests was to verify that the real-time model could accurately predict the effects of a compressor station start up or shut down. Another benefit of running these tests was to increase the operator's confidence in the model.

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