Helium Storage in Cliffside Field

Abstract Since Jan., 1963, the U. S. Bureau of Mines hasbeen injecting crude helium into the Bush Dome structureof Cliffside field for storage in connection with thegovernment's helium conservation program. It is predictedthat during the life of the injection program about 59 Bcfof crude helium, containing 41.5 Bcf of helium, will beinjected. As of July 1, 1966, 15.3 Bcf of crude helium, containing 10.7 Bcf of conservation helium, way in storage. Introduction The Cliffside field is located about 15miles northwest of Amarillo, Tex. Bush Dome, the storage reservoir, is the largest of fouror five secondary domes in Cliffside field andwas discovered in 1924. The dome was originallydeveloped to supply helium-bearing natural gasfor processing at the Amarillo helium plant. Production is from the Brown dolomite formationat about 3,300 ft. Prior to the injection of crude helium, pure helium had been injected and recovered fromunderground storage. The success of that projectand additional studies confirmed that the reservoirwas suitable for storage. Field wells wererecompleted in 1961, and the field was convertedfrom production to a simultaneous production-heliuminjection operation. Wellheads were installedunderground to reduce the possibility of damage, and a control system was installed so that eachwell could be controlled without approaching thewellhead. History of Conservation Helium occurs as a constituent of natural gasin most, if not all natural gas fields in theUnited States. However, fields containing heliumin high enough percentages to make helium extractioneconomically feasible are limited. As gas producedfrom these fields was consumed as fuel, the heliumcontained in the gas was wasted at a rate of 6Bcf/year. This loss of helium through the fluesof gas consumers, coupled with a great increasein helium demand during the 1950's, prompted theBureau of Mines to consider some method of conservinghelium. It was estimated that without conservationthe helium available from known sources would bedepleted in about 30 years. Congress recognized that helium was a valuable, irreplaceable resource and that an adequate futuresupply should be assured, and in 1960 passedlegislation enabling the Secretary of the U. S. Dept.of Interior to enter into long-term contracts for thepurchase of helium for conservation. Contracts torun 22 years, obligating $47.5 million a year for thepurchase of helium, were made with four companies. The private companies constructed five conservationhelium plants in Texas and Kansas. Helium producedby the conservation plants is in crude form, which isessentially a helium-nitrogen mixture with smallamounts of methane and hydrogen. The helium contentof crude helium ranges from 50 to 80 percent andaverages about 70 percent. The crude helium is transported through agovernment-owned high-pressure pipeline for injectionand storage in the Bush Dome structure of Cliffsidefield. Cliffside field is an irregularly shaped highsituated on the south side of the buried AmarilloMountain structure and on the north edge of the PaloDuro basin. Seismic data indicate the presence offour or possibly five secondary domes in Cliffsidefield. The largest of these structures is BushDome which has a vertical closure of about 550 ftand an areal extent of about 11,000 acres. The domehas a steep dip to the north and northwest and agentle dip to the south and southeast. The main gas-producing horizon and also theformation in which crude helium is being stored onBush Dome is in Permian-Wichita-Albany-Wolf-campbeds known locally as the Brown dolomite. TheBrown dolomite, found at a depth of about 3,300 ft, consists largely of dolomite but also containsanhydrite, shale and sandstone stringers. Anhydriteand shale stringers are evident in every well, butindividual stringers cannot be correlated betweenwells. The dolomite is heterogeneous and varies inthickness from 250 to 300 ft. Brown dolomiteporosity obtained from core analysis ranges from4 to 20 percent with a weighted average of about 11percent. Permeability is about 10 md. Immediatelyabove the storage formation is the Panhandlelime formation. This is the caprock of the heliumstorage reservoir. The caprock consists largely ofimpermeable anhydrite and averages about 400 ftin thickness throughout Bush Dome. The top of thePanhandle lime is easily recognizable from well logsand is usually used as a marker for contour mapping. JPT P. 885ˆ