Upstream
and Downstream ...
CWC Gulf
is providing clients with new solutions
for concession acquisition, project viability,
finance, risk and a well co-ordinated
development strategy, both commercial
and political.
The upstream energy market is facing difficult
times. Reserves are becoming more difficult
to locate and more expensive to develop.
As a result, oil and gas companies have
placed more emphasis on managing assets
and streamlining business processes to
maximize profitability. Smaller E&P
companies have built businesses by developing
and operating marginal fields which are
un-economic to the majors and by utilizing
enhanced recovery techniques. Production
and operations managers, as well as engineers
and geologists require constant access
to comprehensive and accurate oil and
gas well information, performance constraints,
benchmarks and service providers in order
to reduce costs and increase production
uptime. Oil and gas executives also need
access to real time asset performance
information and benchmarking indicators
in order to optimize portfolios through
asset management and divestment decision
data.
Economics
of LNG
While industry leaders agree that the
bulk of LNG trade will continue to be
founded on long-term transactions, in
the coming years they expect to see an
increase in short-term LNG trade. This
translates to sales agreements lasting
between one and three years, even spot
trade agreements, and agreements lasting
less than a year. Pricing and contract
structures are likely to become more flexible
to suit market requirements. Producers
are under pressure to cut costs throughout
the LNG chain by adopting a more innovative
approach to both the commercial and technological
aspects of LNG projects. New technologies,
such as floating LNG facilities, are expected
to improve the economics of grassroots
projects. As for new markets, the industry
continues to pin its hopes on China and
India.
About LNG
When natural gas is cooled to a temperature
of approximately -260°F at atmospheric
pressure it condenses to a liquid called
liquefied natural gas (LNG). One volume
of this liquid takes up about 1/600th
the volume of natural gas at a stove burner
tip. LNG weighs less than one-half that
of water, actually about 45% as much.
LNG is odorless, colorless, non-corrosive,
and non-toxic. When vaporized it burns
only in concentrations of 5% to 15% when
mixed with air. Neither LNG, nor its vapor,
can explode in an unconfined environment.
LNG Composition
Natural gas is composed primarily of methane
(typically, at least 90%), but may also
contain ethane, propane and heavier hydrocarbons.
Small quantities of nitrogen, oxygen,
carbon dioxide, sulfur compounds, and
water may also be found in "pipeline"
natural gas. The liquefaction process
removes the oxygen, carbon dioxide, sulfur
compounds, and water. The process can
also be designed to purify the LNG to
almost 100% methane.
LNG Storage
LNG tanks are always of double-wall construction
with extremely efficient insulation between
the walls. Large tanks are low aspect
ratio (height to width) and cylindrical
in design with a domed roof. Storage pressures
in these tanks are very low, less than
5 psig. Smaller quantities, 70,000 gallons
and less, are stored in horizontal or
vertical, vacuum-jacketed, pressure vessels.
These tanks may be at pressures any where
from less than 5 psig to over 250 psig.
LNG must be maintained cold (at least
below -117°F) to remain a liquid,
independent of pressure.
|
LNG
is transported by special vessels |
LNG Cryogenics
The insulation, as efficient as it is,
will not keep the temperature of LNG cold
by itself. LNG is stored as a "boiling
cryogen," that is, it is a very cold
liquid at its boiling point for the pressure
it is being stored. Stored LNG is analogous
to boiling water, only 470° colder.
The temperature of boiling water (212°F)
does not change, even with increased heat,
as it is cooled by evaporation (steam
generation). In much the same way, LNG
will stay at near constant temperature
if kept at constant pressure. This phenomenon
is called "autorefrigeration".
As long as the steam (LNG vapor boil off)
is allowed to leave the tea kettle (tank),
the temperature will remain constant.
If the vapor is not drawn off, then
the pressure and temperature inside
the vessel will rise. However, even
at 100 psig, the LNG temperature will
still be only about -200°F.
