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API 27-33273 1980

API 27-33273 1980-JUL-01 Paraho Oil Shale Workers Occupational Health Study

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Oil shale is one of our largest undeveloped fossil energy resources. Research and development of efficient mining, processing, and refining techniques are continuing in an effort to tap this enormous potential source of crude oil. During this development period, occupational health studies can make important contributions to our knowledge of the working conditions and potential for health problems related to oil shale work. This knowledge can be applied to future facilities and plants as the industry develops.

In late 1977, a proposal was initiated for a joint DOE and American Petroleum Institute (API) project to undertake a medical and industrial hygiene study at the Paraho oil shale facility. This facility is located near Rifle, Clorado, and is leased by Development Engineering, Inc. (DEI), a subsidiary of Paraho Development Corporation. The occupational health study included (1) field industrial hygiene surveys and sampling to assess possible environmental hazards in the workplace and (2) medical examinations of the workers to determine current health status and to establish a data base for prospective epidemiologic studies.

Oil shale is a rock in which the mineral portion is associated with high molecular weight organic material in a complex manner. The mineral portion is primarily a marlstone or mixture of calcium and magnesium carbonates (dolomite) with smaller portions of quartz and silicates. Small amounts of sodium and aluminum minerals also occur as pockets in some oil shale deposits. The organic portion is principally a material called kerogen, which is of such high molecular weight that it is not extractable by ordinary aromatic solvents. A second organic constituent is bitumen, which is extractable by benzene and other solvents.

In order to obtain oil from this material, it is necessary to decompose the kerogen in some manner and convert it into compounds that can be separated from the mineral matter either by distillation or solvent extraction. All processes currently under investigation use heat for this purpose. The heat is usually derived from combustion of a small part of the material in the process.

Separation may be obtained by ignition of the material underground using an external source of fuel, and then establishing a continuous process as the kerogen decomposes and the oil and gases and driven off while the remaining carbon in the oil shale burns to sustain the temperature. This is the in-situ process and requires that the mineral be broken up underground so that air can enter and the oil can escape and be removed through an opening distant from the flame. A modification of this process involves the removal of a portion of the mineral by mining it out and then rubblizing the remaining material by explosives to create a matrix with voids sufficient for air and product penetration. Ignition is done at the top of the matrix with the product being removed at the bottom as the burning interface proceeds downward.

Above ground processing requires removal of the oil shale by a mining operation following by crushing and sizing to an optimal size and then heating in a large vessel called a retort. The heat may be applied by combustion within the retort (direct process) or by mixing preheated gases or solids with the oil shale (indirect process). There are several processes for carrying out this operation using various types of retorts.

The DOE Anvil Points Oil Shale Mine and Retorting Facility near Rifle, Colorado, is situated on the Naval Shale Reserve 1 and 3. Experimental retorts and a small refinery were built by the U.S. Bureau of Mines in 1944 and operated experimentally by the Bureau until 1954. The while site was shut down and moth-balled from 1954 until 1965 when it was leased by a six-company group who again used it for experimental work until 1968 when it was again moth-balled. In 1972 the site was leased by DEI on behalf of the Paraho Development Corporation, for a demonstration project using the Paraho retort. In 1974, a three-year program of engineering, construction, and operation of two Paraho oil shale retorts was organized. Seventeen private companies originally participated in supplying capital for this venture. After this venture was completed in early 1976, the facility was refurbished in preparation for the production of 100,000 barrels of crude shale oil. These production operations, carried out during 1977-1978 were funded by the Office of Naval Research (ONR) and the DOE.