[Editors] MIT math model could aid natural gas production

[Elizabeth Thomson]

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT math model could aid natural gas production
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For Immediate Release
TUESDAY, NOV. 14, 2006
Contact: Elizabeth A. Thomson, MIT News Office
Phone: 617-258-5402
Email: thomson at mit.edu

IMAGE AVAILABLE

CAMBRIDGE, Mass.--MIT engineers have developed a mathematical model 
that could help energy companies produce natural gas more efficiently 
and ensure a more reliable supply of this valuable fuel.

The researchers are now collaborating with experts at Shell to apply 
the model to a natural gas production system in Malaysia.

Natural gas consumption is expected to increase dramatically in the 
coming decades. However, in the short term, demand for this 
clean-burning fuel is highly volatile. Because natural gas is 
difficult to transport and store, energy companies tend to produce it 
only when they have buyers lined up and transportation capacity 
available, generally under long-term contracts. As a result, they 
miss opportunities for short-term sales, and the overall availability 
of natural gas is reduced.

Natural gas companies would like to operate their production networks 
more efficiently and flexibly. But operators can be overwhelmed by 
the sheer number of choices to be made and obligations to be met 
under supply contracts with customers and facility- and 
production-sharing agreements with other companies.

According to Professor Paul I. Barton of the Department of Chemical 
Engineering, the only way for a company to optimize such a 
system-that is, to operate it so as to best meet all obligations, 
objectives and constraints-is to formulate it as a mathematical 
problem and solve it.

"If there were just one or two decisions to make, an engineer could 
do it," he said. "But when you've got 20 valves to set and 50 
different constraints to satisfy, it's impossible for a person to 
see. Computer procedures can take all of that into account."

Barton and chemical engineering graduate student Ajay Selot have 
spent the past two years developing a mathematical model to help 
guide operators' decisions one to three months in advance. The model 
focuses on the "upstream supply chain," that is, the system from the 
natural gas reservoirs to bulk consumers such as power plants, 
utility companies and liquefied natural gas plants.

While other models have focused on optimizing individual subsystems, 
the new MIT model encompasses the whole system. "Ideally, operators 
would like to make decisions based on information from the entire 
system," Selot said.

Based on fundamental physical principles, the researchers' model 
describes gas flow, pressure and composition inside every pipeline in 
the network. Equations describe how the flow properties change as the 
gas passes through each facility along the way. The equations 
interact so the model can track flows and how they mix throughout the 
system.

To be useful in the real world, the model must also incorporate-in 
mathematical terms-the rules from all contracts and agreements. For 
example, what fraction of production must be shared with other 
companies?

Operational constraints must also be included. How rapidly can gas be 
withdrawn from a given well? Further, the company must define its 
goals, such as maximizing production, minimizing total costs or 
scheduling facilities in a particular way.

The final challenge is to "solve the model" so that it defines the 
specific operating choices that will best satisfy the stated 
obligations, constraints and goals. Standard optimization techniques 
cannot handle such a large and complex model. Selot is therefore 
refining and extending standard techniques to solve that problem.

He and Barton are now performing a case study of a natural gas 
production system in Malaysia operated by Sarawak Shell Berhad, 
Malaysia (SSB). They are working closely with field engineers at SSB 
and Shell International Exploration and Production, the Netherlands, 
to build a realistic representation of the Sarawak system-a 
challenge, as the system is the product of decades of evolution 
rather than coordinated planning. All of the system's complexity must 
be reflected in the mathematical model if it is to be of practical 
value to the Sarawak planners.

This research was supported by Shell International Exploration and 
Production through MIT's Laboratory for Energy and the Environment.

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Written by Nancy Stauffer
MIT Laboratory for Energy and the Environment