Survey of Energy Resources 2007
Oil Shale Country Notes
United States of America
It is estimated that nearly 74% of the world's potentially recoverable shale oil resources are concentrated in the USA. The largest of the deposits is found in the 42 700 km2 Eocene Green River formation in north-western Colorado, north-eastern Utah and south-western Wyoming. The richest and most easily recoverable deposits are located in the Piceance Creek Basin in western Colorado and the Uinta Basin in eastern Utah. The shale oil can be extracted by surface and in-situ methods of retorting: depending upon the methods of mining and processing used, as much as one-third or more of this resource might be recoverable. There are also the Devonian-Mississippian black shales in the eastern United States. The Green River deposits account for 70% of US shale oil resources, the eastern black shales for 9%.
Oil distilled from shale was burnt and used horticulturally in the second half of the 19th century in Utah and Colorado but very little development occurred at that time. It was not until the early 1900s that the deposits were first studied in detail by the US Geological Survey and the Government established the Naval Petroleum and Oil Shale Reserves, which for much of the 20th century served as a contingency source of fuel for the nation's military. These properties were originally envisioned as a way to provide a reserve supply of oil to fuel US naval vessels.
Oil shale development had always been on a small scale but the project that was to represent the greatest development of the shale deposits was begun immediately after World War II in 1946 - the US Bureau of Mines established the Anvils Point oil shale demonstration project in Colorado. However, processing plants had been small and the cost of production high. It was not until the USA had become a net oil importer, together with the oil crises of 1973 and 1979, that interest in oil shale was reawakened. In the latter part of the 20th century military fuel needs changed and the strategic value of the shale reserves began to diminish.
In the 1970s ways to maximise domestic oil supplies were devised and the oil shale fields were opened up for commercial production. Oil companies led the investigations: leases were obtained and consolidated but one by one these organisations gave up their oil shale interests. Unocal was the last to do so in 1991.
Recoverable resources of shale oil from the marine black shales in the eastern United States were estimated in 1980 to exceed 400 billion barrels. These deposits differ significantly in chemical and mineralogical composition from Green River oil shale. Owing to its lower H:C ratio, the organic matter in eastern oil shale yields only about one-third as much oil as Green River oil shale, as determined by conventional Fischer assay analyses. However, when retorted in a hydrogen atmosphere, the oil yield of eastern oil shale increases by as much as 2.0-2.5 times the Fischer assay yield.
Green River oil shale contains abundant carbonate minerals including dolomite, nahcolite, and dawsonite. The latter two minerals have potential by-product value for their soda ash and alumina content, respectively. The eastern oil shales are low in carbonate content but contain notable quantities of metals, including uranium, vanadium, molybdenum, and others which could add significant by-product value to these deposits.
After many years of inactivity, interest was revived in the oil shale sector in 2004. A committee was formed by the Office of Naval Petroleum and Oil Shale Reserves and prepared two reports: 1) Strategic Significance of America's Oil Shale Resource, vol. I, Assessment of Strategic Issues and vol II, Oil Shale Resources, Technology and Economics and 2) America's Shale Oil, A Roadmap for Federal Decision Making.
The increasing price of petroleum has encouraged the Government to initiate steps toward the commercial development of the Green River oil shale deposits through the issuance of RD&D oil shale leases. In 2005, nominations for 160-acre tracts of public oil shale lands in Colorado and Wyoming were sought from private companies by the Bureau of Land Management (BLM). By September 2005, 19 applications for leases had been received - ten in Colorado, eight in Utah, and one in Wyoming. After a review of these nominations, five leases were granted in Colorado in late 2006; one lease in Utah received provisional approval (April 2007) and the Wyoming application was denied. All of the successful applicants for the Colorado leases propose to develop in-situ technologies for the recovery of shale oil, whereas the Utah lease applicant plans to use a surface retort. Industry interest in surface mining of oil shale in Colorado appears to be minimal, in view of the problems of possible large-scale environmental degradation of the oil shale lands.
The RD&D leases were issued for a term of 10 years with a possible five-year extension, providing that evidence of diligent pursuit of production of shale oil in commercial quantities is shown. If commercial production is achieved, a preference right for additional acreage of as much as 4 960 acres of oil shale lands may be granted. The RD&D leases include specific requirements of permitting, and monitoring and mitigation of environmental impacts.
Since 1996 Shell Frontier Oil & Gas has been developing a new technique for extracting the oil by in-situ heating of the rock in the Piceance Creek Basin. Shell's patented In-Situ Conversion Process (ICP), which is more environmentally benign and uses less water than conventional methods, involves heating the rock containing the kerogen until it yields a liquid hydrocarbon. In order to trap the oil prior to removal and refining, a barrier of ice between the heated rock and the surrounding area is created by the circulation of a chilled, compressed liquid.
In November 2006, Shell announced that the US BLM had awarded the company three leases on land in the Piceance Creek Basin to conduct further RD&D. This work will begin once the necessary State, air and water permits have been granted.
The estimated total resource of Green River oil shale in the three-state area amounts to about 1.5 trillion barrels of in-place shale oil. Although recoverable shale oil resources have been estimated to be as high as 800 billion barrels, no definitive study has yet been made to substantiate this figure.
By way of enhancing the publicly-available body of knowledge, the US Geological Survey is preparing a database with information taken from the Green River Formation prior to its closure in 1996 and is also acquiring new data and maps. The Office of Naval Petroleum and Oil Shale Reserves announced early in 2007 that the US could be producing oil from shale on a commercial basis in northwest Colorado by 2015.