Solution Mining Aids the L.P.G. Industry

Abstract

Abstract One of the recent developments in the petroleum industry has been underground storage of liquefied petroleum gases (L.P.G.). Because of the high winter and low summer demand, an inexpensive means of large-volume storage is absolutely necessary to regulate supply and demand to make the economics of installing L.P.G. recovery facilities attractive. The most feasible storage zone in Western Canada is an underground salt accumulation of considerable thickness and purity, although old mine excavations and natural caverns have been used. This paper reviews the development of an L.P.G. storage facility at Fort Saskatchewan, Alberta, where a mixed hydrocarbon feed comes in by pipeline and passes through a processing plant to derive marketable propane, butane and condensate. The production of propane and butanes in excess of sales is stored in cavities that were developed in a subsurface salt formation. The caverns are at a depth of approximately 6100 feet in the Fort Saskatchewan area. The leaching method involved the use of concentric strings of pipe and a hydrocarbon fluid for control and roof protection. This paper describes and illustrates the method of mining, associated equipment and materials, and some of the problems encountered during cavern development.. The cost of developing subsurface storage is about 1/15 the cost of surface tanks of similar volumes which illustrates the inevitability of such a system for the future in the rapidly expanding demand for hydrocarbons. INTRODUCTION THE DEVELOP1r ENT of large underground storage caverns for liquefied petroleum gases (LP.G.) has been practiced for many years. Use of these cavities for storage purposes has gained importance in recent years due mainly to the economics and the rising need to regulate low summer and high winter demands. The idea of controlling the shape and size of a cavern dissolved in massive salt has not been a major consideration of most companies engaged in developing underground storage. This has been due, mainly, to an insufficient knowledge of the mining process and the lack of published information dealing with the advantages and ease of controlled mining. This paper describes the facilities, leaching process and other factors involved in developing caverns at Chevron Standard's fractionation facility at Fort Saskatchewan. This facility consists of a pipeline from the Kaybob South gas field, 20,000 barrels of surface storage at the plant site for the raw feed, a fractionation plant and six caverns which will have a capacity of approximately 2 million barrels when completed. The project began in early 1971 and should be complete by the end of 1973. A controlled system for the leaching method was applied by Chevron because of the limited thickness of salt available. Description Of Facility And Purpose The Fort Saskatchewan fractionation and storage facility was built to handle the large volumes of mixed hydrocarbons produced by plants serving the Kaybob South Beaverhill Lake Pool. This large (3.8 trillion cubic foot) gas reservoir, located 150 miles northwest of Edmonton (Fig. 1), is served by three processing plants handling up to 785 million cubic feet of sour wet gas per day.