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Current Events » in reply to Please enlighten me

A good article from the Colorado School of Mines
Larry J — (archived)

Available here. Here's an excerpt:

Shale oil recovery methods. Oil shale must be drilled and blasted. If it is to be processed other than in situ (the method tried by Occidental Petroleum near De Beque), the blasted rock must be loaded and hauled to the processing plant where it is crushed, and then heated. The organic material in oil shale is kerogen. Kerogen can be the first stage of nature's way of producing oil, but it has not gone through the "oil window" of heat, and therefore, to be changed to an oil-like substance, it must be heated to approximately 900 degrees F. By this process the organic material is converted into a liquid, which must be further processed to produce an oil which is said to be better than the lowest grade of oil produced from conventional oil deposits, but of lower quality than the upper grades of conventional oil.

Colorado’s shale oil is chemically “kerogen” – not petroleum. It is not the equivalent of “heavy oil” or “tar”, which are hydrocarbons. An additional hydrogen (H) atom is required to convert kerogen into a hydrocarbon that can be refined into gasoline and other petroleum products. The missing hydrogen is usually supplied from water (H2O) and requires a “pre-oil” plant plus large quantities of water – which is rare in the oil shale regions of semiarid Western Colorado. In order to release hydrogen from water, energy must be supplied. This two-step refining procedure makes the production of gasoline from shale oil prohibitively expensive for practical purposes. The original untreated kerogen shale oil is good only to burn as boiler fuel or as a base for some plastics and other petroleum by-products.

When heated, oil shale tends to expand, so the resulting volume, even after the oil has been removed, may be as large or larger than it was originally. This material must be disposed of, and for a shale oil plant of significant size (e.g. 500,000 barrels/day), the amount of waste material would be enormous. This has to be transported to a proper disposal site. It must be stabilized so it will not contaminate areas beyond the disposal site, because the spent shale has a variety of undesirable mineral compounds which rain will leach. The waste material must be watered and vegetated so it does not blow around.

Two other procedures have been tried to recover oil or gas from oil shales. (Note that small amounts of oil and gas are now recovered by wells from a few places in oil shales. Montgomery Morgan, 1998). Occidental developed an underground operation, which involved excavating a series of small rooms to provide space for oil shale rubble formed by blasting. This was set afire with temperatures reaching 900 degrees F, cracking the kerogen into oil which drained down through rubble pile into a sump. (Chew, in Murray 1974). The Rio Blanco project was designed to test the of nuclear blasts to fracture a gas-bearing sandstone in the Green River Formation, and place it production. Three 30-kiloton nuclear devices were simultaneously exploded in a well at depths 5,840; 6,230; and 6,690 feet. (Weichman, in Murray, 1974). But the results were not economic.

In short, the cost of extraction for shale oil is currently prohibitive when compared to petroleum. There are the costs of extraction, the amount of water needed (and shale oil is often found in arid areas where water is scarce), and then the environmental cleanup costs. Natural petroleum would have to be a lot more expensive before shale oil could be economically viable.

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