Summary
Natural gas is rapidly becoming an even more important resource of energy,
with its share in the world consumption expected to increase dramatically over
the next two decades. Currently, natural gas is transported to the markets by
pipelines and as LNG. Transporting the natural gas by pipelines is convenient
and economically attractive onshore. For the offshore transport of natural gas,
pipelines become challenging as the water depth and transporting distance
increase. LNG, an effective means of transporting gas for long distances across
the seas, constitutes 25% of the world gas movement. But LNG projects require
large investments, along with substantial natural-gas reserves, and are
economically viable for distances of 2,500 miles and beyond.
CNG provides an effective way for shorter-distance transport. The technology
is aimed at monetizing offshore reserves that cannot be produced because of the
unavailability of a pipeline or because the LNG option is very costly.
Technically, CNG is easy to deploy, with lower requirements for facilities and
infrastructure. “Coselle” and “Votrans” are two would-be commercial,
high-pressure gas-storage and -transport technologies for CNG. Technical and
economic analyses of these two technologies were done in this study, and a
comparison is provided. The results show that for distances up to 2,500 miles,
natural gas can be transported as CNG at prices ranging from U.S. $0.93 to
$2.23 per MMBtu compared to LNG, which can cost anywhere from $1.5 to $2.5 per
MMBTU depending on the actual distance. At distances beyond 2,500 miles, the
cost of delivering gas as CNG becomes higher than the cost for LNG because of
the disparity in the volumes of gas transported with the two technologies.
Introduction
Consumption of natural gas internationally has been increasing rapidly,
making it one of the most important energy resources in the world. At the time
of this writing, world consumption of natural gas has touched 100 Tcf, an
increase of approximately 25% in a decade (compared with a 16% increase for oil
and a 5% increase for coal) (Energy Information Administration 2004). Over the
next 20 years, natural gas is predicted to increase its world energy share
substantially from the present 23% (Economides et al. 2000). Much of the
increased consumption is seen to be in electric-power generation, but
transportation will likely be the deciding factor on the actual and potential
dramatic increase.
The lower carbon emissions compared to oil and coal and other reduced
emissions of nitrogen oxides and particulates make gas environmentally
attractive. More important is that the cost of power generation using natural
gas is as much as 50% less than using coal (Oligney and Economides 2002). In
the U.S. alone, there are projections of annual natural-gas consumption in
power generation from 5.25 Tcf in 2004 to 9.5 Tcf in 2024, an increase of 80%
(Energy Information Administration 2006). Similar trends are seen in rapidly
developing parts of the world such as China and Southeast Asia.
This increased consumption of natural gas, along with the anticipated
reduction of the market share of coal and oil, has raised the specter of
shortages in supply in the United States and other nations. With the emerging
demand and with new market opportunities expected to arise, the methods of
transporting the gas from offshore reserves and overseas sources have generated
considerable and renewed interest.
© 2006. Society of Petroleum Engineers
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History
- Original manuscript received:
1 November 2004
- Revised manuscript received:
13 September 2005
- Manuscript approved:
18 September 2005
- Version of record:
20 May 2006
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