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Unconventional oil is oil obtained in a manner that differs from the usual drilling method. Many unconventional oils exist, including oil sand and shale rock, and the term applies more to how the oil is extracted than to the oil itself. In terms of efficiency, yield and environmental impact, unconventional oil is not as good as conventional oil. Conventional oil extraction is turning up less and less oil, though, so many oil drilling companies are looking into alternative ways to get oil.
Kerogen is a material that originates from either plants or animals and has been bacterially altered. Unlike liquid petroleum, which has gone through extreme heat to become conventional oil, kerogen has not gone through this process. By using a heating process, kerogen is converted into an oil-like substance that can be used like regular petroleum. Shale rock, a type of sedimentary rock, contains high amounts of kerogen and is one method of obtaining unconventional oil commonly called shale oil.
Bitumen, more often called oil sand because of its texture, looks much like oil or tar but is neither. It is a semisolid material that contains degraded oil and is composed heavily of sand and clay particles. This method yields little unconventional oil, because 2 tons (1,814 kilograms) are needed for one barrel of oil. The most common way of extracting bitumen is by injecting steam into oil sand, which reduces the viscosity of the bitumen and makes it easier to collect.
Heavy oil is unconventional oil that is similar to conventional oil but much heavier. This is because the lighter hydrocarbons found in conventional oil have degraded, leaving only a heavy substance. To extract heavy oil, dilutants are added to reduce the overall viscosity so the heavy oil can be pumped.
Thermal depolymerization (TDP) is a method that emulates nature and uses different feedstock for unconventional oil. Feedstocks, such as petroleum coke or waste deposits, are added to the TDP unit. By using extreme heat and pressure, the feedstock is processed to create oil. The oil yield differs depending on the feedstock.
While unconventional oil offers different methods for getting oil, it does have environmental hazards. Most of the materials used in unconventional oil drilling and extracting have high amounts of toxic substances, such as sulfur. The areas from where unconventional oils come also are generally more hazardous for workers.