As the demand for natural gas continues to rise, a new way to store liquefied natural gas (LNG) is being explored that would help shorten the time and cut the costs of creating LNG storage space. This new method involves gasifying and warming LNG and then pumping it into undersea salt caverns. Storage is the gas industry’s main tool for managing supply and demand, so using undersea salt caverns may help harness the wholesale price of natural gas.
In 2004, the U.S. Department of Energy (DOE) sponsored testing of a heating and pumping system, known as the Bishop Process, which was invented by William M. Bishop and Michael M. McCall of Conversion Gas Imports (CGI) in Houston, Texas. According to CGI’s Web site, the system receives LNG from a ship, pumps it to cavern injection pressures, warms the LNG to salt-compatible temperatures, and then directly injects it into salt caverns for storage. DOE conducted its tests to determine if LNG could be warmed from -260˚F to 40˚F and then be pumped quickly enough for a tanker to complete the job in one day. LNG must be warmed because the salt in the caverns would crack if exposed to extremely cold LNG, and ice could possibly build up around the transporting pipes.
The tests of the Bishop Process proved that ice would not be a problem. In addition, the system was able to convert LNG to flowing natural gas at rates exceeding 160 million cubic feet/day, meaning tankers could unload in one day. The Bishop Process LNG terminal has many benefits, including it is faster to construct, less expensive to build and operate, significantly more secure, and capable of better storage and delivery than conventional tank-based LNG terminals. The DOE-supported study also identified more than two dozen sites that had suitable salt formations close to transmission pipelines.
“Offshore, out of sight of land, with large-volume gas storage below the sea bedthis may be the ultimate cure for the NIMBY [Not in My Backyard] effect and allow the large-volume importation of LNG without disrupting the coastal port operations,” the DOE report stated.
Salt caverns naturally occur in almost every ocean, although they are scarce in the Pacific. It is estimated that they account for about 5 percent of the United States’ natural gas storage capacity.