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ABS is supporting the safety and security of natural gas storage
in man-made subterranean salt caverns (lower left).
A floating or fixed offshore LNG receiving
terminal (right) can be located near salt caverns and
gas markets, serving differing requirements for offload
rate, storage capacity and send-out capacity. This terminal
concept, one of several proposed concepts, eliminates
the need for large cryogenic LNG storage tanks.
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BS’ expertise with buoy mooring technology
is being tapped to support a cooperative |
government/industry research project to study the feasibility
of storing natural gas unloaded directly from ships into underground
salt caverns. ABS, which has classed some 40 single-point moorings
(SPMs) was invited to assist industry with this pioneering cooperative
research program in gas transport and storage, says William
J. Sember, ABS Vice President of Energy Development.
“The novel concept of storing natural gas in salt caverns
presents an alternative to the construction of new infrastructure,”
said Sember.
The proposed system will use seawater to vaporize liquefied
natural gas (LNG), unload the product at an SPM terminal and
inject it into underground salt caverns, avoiding the use
of above-ground tanks.
“The proposed system would bring two distinct benefits
to the industry. Offshore LNG receiving is a ‘coming wave’
for reasons of increased safety, security and logistical practicality.
Safe underground storage eliminates the need for cryogenic liquid
storage tanks at land-based LNG receiving terminals,”
he said. |
Spearheaded by Conversion Gas Imports (CGI), the joint industry
program receives majority funding from the US Department of Energy.
ABS joins a cross-section of industry leaders participating in the
study, including AGL Resources, Bluewater Offshore, BP, Dominion,
EnCana, ExxonMobil, FLUOR, FMC Technologies, HNG Storage, Marathon,
Paragon Engineering Services, PB Energy Storage Services and SBM-Imodco,
among others.
With many years of LNG technical experience, ABS will provide enormous
value to the project, says Mike McCall, CGI President and CEO.
“In moving from the concept stage, through the research process
and finally to commercial application, the independent analysis
and expertise of ABS is critical to the project,” said McCall.
McCall advises that an important but lesser-known aspect of the
concept is that the salt caverns are man-made facilities, not natural
formations, constructed through drilling operations and solution
mining.
Solid subterranean salt formations are drilled out and injected
with seawater or fresh water if onshore. Saturated brine is then
displaced, leaving man-made caverns with sizes and shapes specifically
engineered for hydrocarbon storage needs. This method is currently
employed by the US Strategic Petroleum Reserve, in various locations,
for approximately 650 million barrels of crude oil.
Underground salt caverns are a logical way to use an indigenous
storage medium for natural gas, says Lance Van Anglen, CGI Vice
President for business development.
“Our goals are security, economy and capacity. Some of these
salt formations are miles across and have huge capacities. Underground
storage for natural gas can be accomplished at relatively low costs,
and because salt becomes a ‘plastic’ substance at certain
temperatures and pressures, these spaces are sealed tanks, like
huge pressure vessels. You can’t get safer,” he said.
The safety, security and economy of adapting this existing storage
method for natural gas depends upon the single-point mooring of
LNG vessels followed by offshore delivery and regasification, says
Sember.
Conceptual plans for the CGI project call for an offshore receiving
terminal at a proposed location on Vermilion Block 179 in the Gulf
of Mexico. Two manned, bridge-linked platforms installed in approximately
100 feet of water would receive LNG from a weather-vaned SPM terminal
approximately 6,400 feet away.
The patented process would employ high-pressure pumps and high-capacity
heat exchangers to heat LNG into a dense phase gas, allowing for
direct unloading into underground salt caverns at a rate comparable
to conventional liquid offloading.
Earlier this year, ABS classified the
world’s first offshore LNG deepwater port buoy.
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