Oil shale is an organic-rich sedimentary rock containing solid, combustible organic matter in a mineral matrix. The organic matter, often called kerogen (a solid mixture of organic chemical compounds), is largely insoluble in petroleum solvents, but decomposes to yield oil when heated.
How Do We Get Oil from Oil Shale?
Extracting oil from oil shale requires conversion of the solid hydrocarbons in the rock to liquid form, so that they can be pumped or processed. Oil shale must be mined using either underground or surface mining methods.
Shale oil extraction is usually performed above ground by mining the oil shale and then treating it in processing facilities. Some newer technologies perform the processing underground by applying heat underground and extracting the oil via oil wells.
After mining, they must undergo retorting, in which the rocks are heated to a high temperature to separate and collect the resultant liquid. This chemical process called pyrolysis, in which extreme temperature is applied in the absence of oxygen to produce chemical change of the shale. In that high temperature (about 700 °F), kerogen present in the shale liquefies to yield oil.
Status and Contribution
While oil shale is found in many places worldwide, by far the largest deposits in the world are found in the United States in the Green River Formation, which covers portions of Colorado, Utah, and Wyoming. Estimates of the oil resource in place within the Green River Formation range from 1.2 to 1.8 trillion barrels, though not all these resources are recoverable.
USA accounts for 62% of the world oil shale resources, and USA, Russia and Brazil together account for 86% in terms of shale oil content. Other countries with significant oil shale include Congo, China, Morocco, Italy, India, Jordan, Canada and Israel.
Advantages of Oil Shale
- Potential to produce a superior liquid-fuel product.
- Low sulfur content and therefore less air pollution
- Abundant availability in countries such as USA that have the highest need for oil
Disadvantages of Oil Shale
- Costs of fuel production from oil shale have not yet been fully evaluated.
- Disposal of the used shale could create ecological problems. Some studies have revealed soil and groundwater contamination to various degrees by chemicals or pollutants from the oil shale tailings.
- Other possible ecological problems are noted below:
- Large Land and Infrastructure Requirements - Regardless of the method of development, oil shale would require significant new industrial infrastructure. Roads, power plants, power distribution systems, pipelines, water storage and supply facilities, and construction staging and storage areas would impose additional demands on the landscape.
- Requirement of Large Amounts of Energy - Extracting oil from rock requires massive amounts of energy. A 100,000 barrel-per-day oil shale operation would typically require 1,200 megawatts of electricity, which would require a large new power plant. This power plant would consume millions of tons of coal each year, greatly contributing to pollution.
- Effects on Fish & Wildlife Habitat - Many land and aquatic species including native fish could be seriously impacted by a full-scale oil-shale industry.
- The complete technology for cost-effective mining and oil extraction from oil shale has not yet been fully developed.
See alsoOil Shale @ Energy Minerals Division - A Division of the American Association of Petroleum Geologists