A mathematical method for transient optimization was presented with hypothetical examples at the 2000 PSIG conference. We saw that this advance in technology combined with the completion of the Vector pipeline provided a fortuitous opportunity to test its applicability in the real world. Vector is a newly constructed natural gas pipeline, approximately 350 miles long, with 5 supply/delivery points and 1 compressor station. The design flow rate is 750 MMSCFD. The pipeline will be expanded to a design flow rate of 1200 MMSCFD with up to 10 supply/delivery points and 2 compressor stations in the near future. The gas controller has control of the compressor stations only. The interconnecting companies control the supply and delivery flow rates, and the pressures are limited by contractual minimum and/or maximum values. Transient optimization has the potential to allow the operator to maximize the economic return from the pipeline operation. This paper presents results pertaining to :
Fuel and energy optimization
Survivability under abnormal operating conditions
Evaluation of spot market opportunities
Optimization of facility expansion or additions
These results are based on actual pipeline operating data, actual nominations, and a full non-linear transient pipeline simulation. The optimized solutions are compared with choices made by human gas controllers using a predictive simulation that has been validated against real operating conditions. The paper concludes by outlining the future direction of Vector's transient optimization efforts.
Steady state optimization has been used in the natural gas pipeline industry for about a decade. Use of this technology has been shown to provide up to 25% fuel savings by allowing the gas controllers to select a more efficient combination of compressor and regulator setpoints. Steady state optimization works well for pipelines that remain in steady state during operation. With the advent of deregulation, short nomination windows and interconnects to peak shaving power plants, many pipelines cannot operate in steady state. Steady state optimization tools may, therefore, no longer provide the complete solution. The gas controllers will consequently face an increasingly difficult task because they likely must continually adjust setpoints to meet changing contracted loads. Pipelines that do not operate in steady state may benefit from optimization in a transient environment. Transient optimization has the potential to provide a pipeline operator with a tool that can be used to :
Optimize fuel and energy usage
Determine if abnormal operating conditions are survivable
Manage or minimize curtailment
Evaluate spot market opportunities
Optimize facility expansion or addition designs 3 Last year
Rachford and Carter [PSIG2000-0004] presented methods used for transient optimization and applied the results to sample scenarios on a hypothetical pipeline. This paper will summarize the results of a study by Enbridge Pipelines, Inc and Stoner Associates to determine if this new technology is viable as an operating tool for the Vector pipeline.