Potential shale oil recovery methods in the Green River Formation and associated environmental problems
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Date
1980-12
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The Ohio State University
Abstract
The United States faces a serious energy crisis and needs to develop new long term domestic sources of energy. One important and untapped source is oil shale. Tapping this resource is an alternative way to lessen U.S. dependence on foreign oil and become more self sufficient. The oil shale, an oil bearing rock that fills the uplands of Colorado, Utah, and Wyoming, contains an estimated 1.8 trillion barrels of oil, or three times the known reserves of the Middle East. At the current rate of consumption, that amount of shale would supply U.S. needs for more than a century. Although oil shale companies know where to find their fuel, they differ on the best way to get it out. The original idea of the oil shale developers relied on so-called surface retorting technology. The shale was strip mined, crushed, and then heated to very high temperatures in huge chambers. The temperature was kept at about 900°F, and this process was called "retorting." This high temperature breaks down the rock's solid hydrocarbon component, kerogen, into oil. The raw shale oil is then cleaned for use as refinery feedstock. To obtain increased yields, cut mining and processing equipment costs, reduce spent shale surface disposal, and limit pollutants emitted in the air, the competitive technology developed the "modified in situ" method below ground. This method extracts shale oil from rock by heating it in underground chambers called retorts. Explosives are detonated in the retorts to reduce the shale to rubble. The shale heap is then lit, and the fire is drawn down through the chamber. The intense heat of the blaze frees the oil from the rocks; then it settles to the bottom and is collected for refining into the desired hydrocarbon products. The greatest unknown about shale-oil production is its impact on the environment. Conservationists claim that one to five barrels of water are required for each barrel of oil extracted from shale. Critics also complain about the release of salts and arsenic into the region's groundwater from surface runoff of the piles of leftover shale rubble. The air could become filled with dust from all the rock that is being unearthed and processed. The final, but poignant protest, concerns the scenic destruction of the Rocky Mountain Valleys. Piles of spent shale residue could clog the valleys if mass stabilization is not accomplished by contouring and planting the dump with local grass and wildflowers. This is a big problem considering the fact that a 400,000 bbl-a-day industry requires 500,000 tons of shale to be mined and retorted. This paper will attempt to address and clarify these problems.