Peace Pipe Line Ltd. operates a pipeline network carrying a wide range o f hydrocarbon liquids. A transient non-iterative pipeline model has been developed by integrating the governing equations f o r conservation o f mass and momentum over a control volume and by linearizing the non-linear terms. The scheme is implicitly mass conservative and the temporal terms essentially removes the limitation on the size of the time step common to well known explicit type schemes and removes the need to iteratively solve the non-linear equations common to non-linear implicit schemes. The method is described and test results are presented.
Peace Pipe Line Ltd. owns and operates a pipeline system in northwestern Alberta, Canada which gathers and transports crude oils, condensates and gas plant liquids to refineries and other pipe line companies in Edmonton. The system consists of approximately 2100 kilometres o f pipe ranging in diameter from 76 mm to 508 mm. The products, which range from Non-Newtonian crude oils to ethane rich NGLs, are batched through the system with numerous intermediate blending points and minimum product storage. The system is controlled from Edmonton via a SCADA system consisting of dual Digital Equipment Corporation POP 11/44 and PDP 11/73 computers with 85 remote terminal units distributed on company owned microwave and leased land lines. In recent years, the company has been transporting larger volumes of compressible products and found its material balance and batch tracking calculations to be inadequate. Accordingly, the company undertook major projects in 1985 and 1986 to upgrade its SCADA and communication systems and to undertake the in-house funding, management and development of a transient pipeline model. The work undertaken by the company has been extensive and included:
Expansion/modification to the company's radio system to support additional telemetry channels.
Rewriting RTU and host software to support custom report-by-exception protocols with synchronized data capture.
Inter-processor data link development between the SCADA and modelling computers.
In-house software development of display, logging and operator entry software associated with the model.
Laboratory analysis work to define fluid properties and define appropriate equations of state.
Field instrumentation additions.
In-house development of the mathematical model.
Field testing and integration.
This paper presents the numeric modelling scheme developed by Peace Pipe Line's in-house consultants, Quantel Engineering and PHH Engineering Ltd. The model was designed to meet the following specifications:
Simulation of 30 seconds of real time for approximately 1000 kilometres of pipeline in less than 15 seconds on a VAX11-750.
A spectrum of liquid products ranging from compressible ethane rich NGL to crude oil.
The capability to accommodate such devices as inline pump stations, block valves, check valves and pipeline laterals.
Batch tracking capability without restriction on the number or movement of batches.
It is believed that two fundamental features distinguish this scheme from those previously developed:
An implicit mass conservative scheme has been developed by formally integrating the governing equations over a control volume.