ABSTRACT

Around 1990 Columbia Gas Transmission Corporation (TCO) started a modeling project that envisioned the following models:

  1. Real-Time Model - Transient Model that runs 24 hours a day based on SCADA data.

  2. Predictor Model - Transient Model that runs from the current state or a historical state into the future assuming certain changes like starting and stopping compressor units.

  3. Auto-Predictor Model - Transient Model that runs automatically every hour for 4 hours into the future assuming no changes to the current state except for market changes.

  4. Load Forecaster - System to predict markets and supplies on an hourly or daily basis.

  5. Trainer Model - Same as a predictor model except it is used as a tool to train Gas Controllers by making the model look like SCADA.

  6. Optimizer Model - Steady-State Model that optimizes fuel based on real-time data or historical data.

This paper describes the results (successes and failures) for each model. It will focus on Real-time Models and Fuel Optimization. The Real-time Models have provided many benefits that have enabled our design and actual operations to match more closely. This paper discusses the problems associated with applying a steady state tool (Optimization Models) to actual transient operations. It shows a comparison of TCO's 1997 fuel costs to 1998 fuel costs and discusses how changes in fuel usage effect our customer's rates and compressor costs. As indicated in the paper our Predictor, Trainer and Load Forecasting Models have not been as successful due to various reasons. We have also included some comments on the PI Historian System. This system has increased our productivity by making historic and real-time SCADA data available via Excel. 3 Columbia Gas Transmission System Columbia Gas Transmission Corporation (TCO) operates over 12,500 miles of Storage and Transmission pipeline in the North Eastern part of the U.S. The primary supply is from Columbia Gulf Transmission in Kentucky with deliveries in the states of WV, KY, OH, PA, VA, MD, NY, NJ, DE, NC and DC. We operate 140 compressor stations with 585,000 total horsepower. TCO has over 3,600 storage wells that store 660 Bcf of which 240 Bcf is annual turnover. The Design Day Storage Withdrawal is 4.5 Bcf. There are over 31,000 gas production wells and over 2,500 delivery meters connected to our system. The annual deliveries total over one trillion cubic feet. (1) Real-time Model The real-time model has provided many beneficial results by providing information that is not available from SCADA. Compressor fuel costs, compressor fuel rates, pipeline flows, pressures, and velocities for stopple jobs are just some examples of the types of data that the real-time model can display. The real-time model has also been used to make our system design match actual operations. One example of this is determining pipeline efficiencies. With these pipeline flows, we have been able to calculate the actual pipeline efficiencies for our main pipeline segments. Locations with low efficiencies create an additional pressure drop that reduces capacity.

This content is only available via PDF.
You can access this article if you purchase or spend a download.