Abstract
In China, annual natural gas consumption is over 67 billion cubic meters
with an expected growth rate of 10% per year. Most of the gas is transported
from well heads to markets over cross-country gas networks, which requires
construction of the West to East Gas Network--one of the largest gas networks
in the world. Presently, the network is comprised of four large-diameter
pipelines and will include most major gas pipelines in China in the future. The
network distributes approximately 30 x 109 m3 gas per year, of which
3% to 5% is burned to power the gas transportation. At current gas prices, gas
transportation costs are roughly 350 million per year, which is a considerable
cost that could be reduced by improvements in network design and operation.
This paper reports on a study aimed at optimizing the network to minimize
its energy consumption and cost. The large size and complex geometry of the
network required breaking the study down into simple components, optimizing
operation of the components locally, re-combining the optimized components into
the network and optimizing the network globally. This four-step approach
employed four different optimization methods, penalty function method, pattern
search, enumeration and non-sequential dynamic programming, to solve the
problem. The results show that cost savings, because of global optimization,
are reduced with increased throughput. For example, increasing the gas rate
from 67 – 90 million m3/d would reduce operational cost savings
because of optimization from 23% – 1.15%. Moreover, the study shows that if the
compressors were fully loaded at their maximum rating, the optimized operation
would approach the one being presently practiced. Thus, the optimization is
effective and much needed when the system does not work at its maximum
capacity, a typical case in the present operations of Chinese gas networks.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
2 April 2008
- Meeting paper published:
18 June 2008
- Revised manuscript received:
15 February 2010
- Manuscript approved:
17 February 2010
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