A. The Need for Gas Storage

Natural gas--clean, easily handled and inherently economical--is a very popular fuel, particularly for space heating Residential and house-heating customers of gas in the United States now number 28.3 million and are

expected to number 43.3 million by 1980.1 This consumption is, however, highly variable. Extremely cold weather creates a demand for several times as much gas as is needed on a warm day, and the gas supplier must almost instantaneously satisfy the "peak" demand. To do this when the source is a long distance from the point of consumption, as it usually is, it is necessary for the supplier to have gas stored near the market or to reduce or stop delivery to industrial consumers. The ability to meet and satisfy market fluctuations without inconvenience at acceptable cost levels is advantageous to both consumer and seller. To build long-distance gas transmission systems with enough capacity to handle peakdemand gas would be decidedly uneconomical.

Adequate gas storage capacity satisfies seasonal as well as "peak day" demand fluctuations. During low demand periods, the capacity of the transmission system can be used to supply the consumers and to fill the storage reservoir. During high demand periods, the deliverability needed in addition to transmission system capacity can be furnished by withdrawing from storage. Thus, the transmission system can be operated at or near capacity and gas can be accepted from the wellhead at a fairly constant rate.

In general, without economic storage facilities, natural gas would not be nearly as competitive as a source of energy away from areas where it is produced, and hence, might not be the attractive national commodity that it is today. It should be remembered that possible savings resulting from nuclear storage would be reflected in reduced gas prices and would accrue primarily to the consumer rather than to the supplier. Gas utilities are allowed by regulatory authorities to earn only a specified rate of return on their investment. Because gas is a basic form of energy, it has an exponential benefit on regional economy where it is available at low cost.

As of January 1, 1966, there were 308 underground gas storage reservoirs, operating or under construction, in 25 states with a total capacity of 4.3 trillion

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standard cubic feet (measured at 14.73 pounds per square inch pressure and 60° F). Domestic gas storage represents a capital investment of $1.25 billion." Of the 293 underground storage reservoirs fully operational, there were 238 depleted dry-gas reservoirs, 9 depleted oil and gas reservoirs, 7 oil reservoirs, 37 aquifers, one solution cavity in salt, and one mined cavern (coal mine). 2 Most of the underground storage is located near large markets. But storage in producing areas also is used to smooth out seasonal fluctuations in demand and for various other purposes. Figure 1 shows locations of existing underground gas storage reservoirs in the United States.

Capacities of storage reservoirs range from less than 100 million cubic feet to more than 100 billion cubic feet--average capacity is about 15 billion cubic feet. Most storage reservoirs are at depths less than 5,000 feet with maximum pressure approximately the same as the original reservoir pressure--usually hydrostatic pressure (0.43 psi per foot of depth).

Under consideration for many years and gaining in popularity is the storage of liquefied natural gas (LNG) at a temperature of -260° F in aboveground or sunken vessels. Four such cryogenic plants are now operating in the United States and six others are being built or have been proposed.

Having established the importance of gas storage and recognizing the continuing need for more storage capacity, the availability of storage reservoirs for future gas industry growth must be examined. Naturally, justification for a storage facility and determination of what type is best at a given location are based on economics. Now, a new type of gas storage reservoir--the chimney created by an underground detonation of a nuclear explosive--is available for consideration along with the conventional types. The application was first suggested by the Columbia Gas System. The use of nuclear data to design such a system was first published by Boardman and Toman of LRL. Economic data was presented in a paper by Witherspoon. 4

Some areas have depleted or nearly depleted oil and gas fields that can be converted to storage reservoirs. However, underground formations suited for this type of storage are not present in all parts of the United States and very few are near the gas markets. Figure 1, besides showing gas storage locations, shows major oil and gas producing areas.

Few

Some parts of the United States have underground salt formations in which storage cavities may be leached. In some places aquifers, suitable for gas storage reservoirs, are known to exist or may be found at moderate expense. But, if much exploration is needed, if reservoir integrity is questionable, or if salt effluent disposal is a serious problem, cost may be prohibitive. depleted fields, salt bodies, or well-defined structures for aquifer storage are located near the points of major consumption of gas, and certainly the obvious and inexpensive facilities already are in use. Massive granites and thick shale deposits located near major gas markets appear to be among the prime prospects for nuclearformed storage cavities. Nuclear storage cavities also may be developed in areas where natural reservoirs have been found but are of insufficient quantity to meet future needs. Such a site is recommended for the Ketch experiment.

Primary research and development is carried out at Livermore, California, by the Lawrence Radiation Laboratory, which is operated by the University of California, for the Atomic Energy Commission. Other research work is underway by the Sandia Corporation, Albuquerque, Oak Ridge National Laboratory; Los Alamos Scientific Laboratory; Savannah River Laboratory; the U S. Bureau of Mines; and the U. S. Geological Survey. In addition, a number of private companies have cooperated with the AEC in carrying out Plowshare research work. The AEC approach has been twofold:

(1) to establish a usable body of quantitative information about the effects of nuclear explosives when fired in various types of rock, and

(2) to work closely with industry in evaluating potential uses of these effects in specific applications.

The nuclear explosive is basically a source of energy just as coal and oil are sources of energy that can be made to do work. It is, however, far more compact and powerful. It may be used for commercial purposes in two basic ways--to make craters and to break rock underground. Craters made by nuclear explosions could be used for water aqueducts, highway cuts, canals, harbors, and overburden removal from mineral deposits.

An explosive when detonated deep underground could be used to break and fracture rock containing valuable minerals so that the rock could then be mined

more easily, or so that solutions could be used to dissolve the minerals out of the ore without further moving it. Oil shale broken in this manner may be amenable to retorting in place. If rock far underground containing oil or gas is broken, it is anticipated that the fluid will flow more freely, making it possible to recover economically the oil or gas which does not at present flow into wells at an acceptable rate. A joint AEC-El Paso Natural Gas USBM experiment, known as "Gasbuggy,"6 to test the application of nuclear explosions to stimulate flow of natural gas has been scheduled for the fall of 1967. Void space created in a similar manner could be used to store or dispose of gases and fluids.

As a result of nuclear experiments by the AEC, a significant body of data related to the physical effects produced by nuclear explosions in various rock types has been accumulated. 7,8,9,10,11,12 The data obtained from these studies coupled with laboratory experiments and theoretical investigations, including mathematical models constructed with computer codes, make it possible to predict certain physical effects with fair accuracy. While such data provide an indispensable base for evaluating possible industrial applications, only an actual nuclear explosive experiment in an industrial situation can truly evaluate the method. The Project Ketch experiment would provide an opportunity to evaluate the technical and economic feasibility of the underground gas storage application.

C. Availability of Explosives

At the present time, the AEC is not authorized to supply nuclear explosives and related services on a commercial basis. The AEC can, however, under the Atomic Energy Act of 1954, utilize nuclear explosives in cooperative research and development arrangements with industry, including demonstrations of particular applications. At such time as Plowshare technology advances to the stage where it is economically and technically practicable, and there is an active industrial demand for explosives, Congressional action would be required to make nuclear explosives available for commercial purposes. Under any foreseeable circumstances, the Federal Government is expected to retain certain responsibilities for transportation and detonation to assure the safety of the general public. In order to assist industry in evaluating possible future uses, the AEC published in 1964, a list of projected charges for nuclear explosives as a guide in evaluating their use in Plowshare applications. Table I shows charges for specific yields picked from the published chart. The AEC believes that the projected charges are sufficiently representative of the future situation to warrant their use in feasibility studies. These charges cover nuclear