Eminence Dome - Natural-Gas Storage In Salt Comes of Age
Authors: Allen Kermit 
Published: December 2007

These two salt-dome caverns in Mississippi have been solution mined specifically for storing natural gas under pressure. The pressure storage allows the gas to flow freely from the caverns as needed and keeps the water content of the produced gas at a minimum.

Introduction
By 1990, the U. S. will need annually almost three times as much natural gas as was sold during 1970. To meet such consumer demands during peak periods, huge storage facilities are needed. Solution-mined caverns constructed in naturally occurring subsurface salt formations has the potential for providing adequate storage. This concept has been providing adequate storage. This concept has been proved by the successful operation of several such proved by the successful operation of several such caverns in Canada and the U. S. Salt suitable for solutioning caverns is found in either of two forms salt domes and bedded salt deposits. There are 329 proved salt domes in the Gulf Coast area. Bedded salt deposits have been found in various parts of the U. S.
Storage of gases and liquid hydrocarbons in solution-mined salt caverns was conceived during World War II, and by 1950 the use of such caverns in the U.S. was extensive. For more than 15 years, salt caverns have been used for storing liquefied petroleum gases such as propane and butane. petroleum gases such as propane and butane. The caverns are constructed by injecting fresh water into a salt formation and removing the resulting brine. A recent storage survey lists more than 500 of these caverns in operation, with a total storage capacity in excess of 5.25 billion gal. Only seven of these caverns, however, were developed for the storage of natural gas.
The first use of a solution-mined salt cavern for storing natural gas was in 1961 when Southeastern Michigan Gas Co. leased, from the Morton Salt Co., and converted an abandoned salt cavern formed by routine brine production. The cavern, near Marysville, Mich., had a working capacity, after conversion, of about 341 MMcf of gas at a wellhead pressure of 1,100 psia and a minimum line pressure pressure of 1,100 psia and a minimum line pressure of 150 psia.
The first such cavern created specifically for the storage of natural gas was constructed by the Saskatchewan Power Corp. and became operational in 1961 The 290,000-bbl cavern, located in Melville, Sask., was constructed in the Prairie Evaporite salt formation at a depth of approximately 3,700 ft.
In the U.S., the first solution-mined salt cavern constructed specifically for the storage of natural gas was completed in the Eminence Salt Dome in Covington County, Miss., in 1970 by Transcontinental Gas Pipe Line Corp. After salt domes in Louisiana, Mississippi, and Alabama had been thoroughly investigated, Eminence Dome was chosen because:
a seismic survey of the dome indicated sufficient salt for the caverns and for future enlargement; the salt was relatively shallow, with the top of the dome only about 2,400 ft below the surface; there was an adequate supply of fresh water for salt leaching brined-isposal wells could be completed in formations on the flank of the dome; enough land was available for all surface facilities; and the dome was near Transco's pipeline.
Each of the caverns in Eminence Dome is operated "brine free"; that is, natural gas is injected into the caverns under pressure, which then causes the gas to flow from the caverns as needed.
JPT
P. 1299