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Oil & Gas Resources

 

Oil Shale

Oil shale was first recognized in Nevada in the Elko area in 1875 and has since been recognized
in other areas. Between 1917-1924, the Catlin Shale Products Company at Elko produced about
12,000 barrels shale oil, but the enterprise was a commercial failure. The products, gasoline and
various lubricants, were of low quality. The following is the Executive Summary from a 1981 re-
port by the Mineral Management Service of the Department of the Interior which summarizes oil
shale in Nevada.

This report is the result of an investigation done through a cooperative agreement made in Aug-
ust 1981 between the USGS, Conservation Division (now Minerals Management Service) and the
Nevada Department of Energy. The purpose of this agreement was to provide funding to invest-
igate and to analyze occurrences of oil-shale resources and their development potential in the
state of Nevada. Since the USGS was already involved in oil-shale studies in northeastern Nev-
ada, the additional funding was applied primarily to a shallow exploratory drilling program used to
better delineate oil-shale deposits near Elko, Nevada. The original source of the funding, in the
amount of $70,000, was the U.S. Department of Energy.

The United States is heavily dependent on oil and natural gas as a primary source of energy and associated products. Despite intermittent fluctuations in petroleum supplies, oil is a finite resource. In the future, as domestic petroleum supplies dwindle and recovery increases in cost, other alternative energy sources such as oil shale may become increasingly more attractive. Although oil shale has not yet achieved successful commercial production in the United States, oil shale should be considered as a future energy resource.

Oil shale is a fine-grained sedimentary rock that yields substantial quantities of oil when heated to high temperatures in a closed retort (destructive distillation). Kerogen is the solid, insoluble, organic material in the shale that can be converted to oil and other petroleum products by pyrolysis and distillation.

Major resources of oil shale occur in ancient lakebeds of the Green River Formation in Colorado, Utah, and Wyoming. Although the resource potential of Nevada oil shale is comparatively minor, relatively little detailed geologic study has previously been devoted to Nevada's oil shale. This report surveys potential oil-shale resources located in northeastern Nevada.

Oil shale in Nevada is primarily associated with rocks now designated as the Elko Formation. Other rock units in Nevada also contain organic-rich deposits that have some minor potential for oil-shale resources; however, they have been discussed in this report mostly because of their significance as conventional oil and gas source rocks for petroleum reservoirs in Nevada. Of these rocks with minor interest for oil shale, the most promising formations include the Vinini and the Woodruff Formations.

The Vinini and Woodruff Formations locally contain kerogen-rich, marine deposited shales that have high concentrations of heavy metals such as vanadium, selenium, and zinc. Although the Vinini and Woodruff Formations locally have shales that yield from a few gallons to as much as 15 to 30 gallons of oil per ton, oil yields are lower on the average. However, the possibility of metal extraction as a byproduct of oil-shale development may make these formations attractive for development in the future.

The Elko Formation contains oil-shale deposits of primary significance in the state of Nevada. A minimum geologic age determined for the Elko Formation is latest Eocene or earliest Oligocene, or about 37 million years old. oil shale in the Elko Formation was derived from the accumulation and preservation of mineral sediments and organic materials deposited in an ancient lake or lakes. Subsequent erosion and faulting have disrupted the original lateral continuity of these oil-shale bearing deposits and left only scattered remnants exposed in mountain ranges, or deeply buried in sedimentary basins in northeastern Nevada. Scattered remnants of the Elko Formation occur over a north-south elongated area about 100 miles in length and 30 miles in width, confined to Elko County.

Detailed surface geologic studies and sampling of the Elko Formation have been conducted at three localities in Elko County: near Elko; in the Pinion Range; and in Coal Mine Canyon. of these three areas, the richest oil-shale deposits occur in the Elko area. Informally designated members 2, 3, and 4 of the Elko Formation near Elko contain oil shale. On the basis of Fischer-assay determinations of oil yield on continuous core samples from the Elko area, total in-place shale oil in members 2 and 3 has been calculated as 600 million barrels. Of this total, 228 million barrels are from beds averaging at least 15 gal/ton over a 15-feet thickness; the minimum classifiable standard for prospectively valuable oil-shale deposits. The remaining approximately 373 million barrels of in-place shale oil has been calculated for low-grade shale of member 3 that averages only 5 gal/ton over a thickness of 260 to 280 feet. Because of high energy demands in mining and processing of oil shale, shales yielding less than 10 gal/ton are not considered to be of sufficient richness to approach present economic development. Therefore, the 228 million barrels of shale oil in member 2 of the Elko Formation is considered to be the present shale-oil resource for the Elko area.

Despite the richness of oil-shale deposits of member 2 of the Elko Formation in the Elko area, the present economic development potential of this deposit is low. Present economic conditions of tight money, high interest rates, and escalating costs of construction have plagued commercial development of all oil shale in the United States, including rich deposits of the Green River Formation. In addition, lower world crude oil prices and decreased domestic crude oil consumption has decreased the present potential for shale oil to compete economically with conventional petroleum sources.

Aside from economic conditions, the stratigraphic and structural complexity of the Elko Formation would be another major disadvantage to development. The close proximity of the town of Elko to the oil-shale deposit puts other serious constraints on the development of that resource. Environmental problems, conflicts with Present land use and water availability, and development of technologically and socially acceptable mining and retorting methods are all factors that would have to be weighed if this oil-shale deposit were to be economically developed on a commercial scale. Although there are notable quantities of shale oil in the Elko Formation near Elko, and more resources may be discovered buried within sedimentary basins in northeastern Nevada, the commercial development of these resources is not likely in the foreseeable future.

Several open-file reports concerning oil shale are available on our website. The GBSSRL also has a number of unindexed, generally old reports dealing with oil shale in Nevada.

>> NBMG publications about oil shale


Coal

To date, no viable commercial deposits of coal have been found in Nevada. The known coal deposits are small and low grade and are generally associated with Tertiary lakebed deposits. Numerous unsuccessful attempts have been made to mine Nevada coal, but the deposits have proven to be too small and impure. Coal is described in NBMG Bulletin 65, Mineral and Water Resources of Nevada, and NBMG Open-File Report OF85-5, A First-Stage Study of Nevada Coal Resources, both of which are available at the NBMG Publication Sales Office.


Natural Gas

Hydrocarbon-bearing gas has been reported from seeps and water wells in several counties. A natural gas seep near Soda Lakes in Churchill County was filed on in 1865, and in the early 20th century, some ranch houses near Stillwater were using gas from shallow (about 300 feet) wells for heating and cooking. This gas was largely methane from organic rich sediments. To date, the only appreciable amounts of gas found have been at the Kate Spring Field in Nye County. This field is presently annually producing less than 8,000 thousand cubic feet of gas, which is being used to operate equipment in the field. Natural gas is discussed with the same references noted for oil below.