World Energy Resources 2013 report by the World Energy Council uses the term "tight oil". Oil shale Oil shale is an organic-rich fine-grained sedimentary rock containing significant amounts of kerogen (a solid mixture of organic chemical compounds) from which technology can extract liquid hydrocarbons (shale oil) and combustible oil shale gas. The kerogen in oil shale can be converted to shale oil through the chemical processes of pyrolysis, hydrogenation, or thermal dissolution. The temperature when perceptible decomposition of oil shale occurs depends on the time-scale of the pyrolysis; in the above ground retorting process the perceptible decomposition occurs at , but proceeds more rapidly and completely at higher temperatures. The rate of decomposition is the highest at a temperature of to . The ratio of shale gas to shale oil depends on the retorting temperature and as a rule increases with the rise of temperature. For the modern in-situ process, which might take several months of heating, decomposition may be conducted as low as . Depending on the exact properties of oil shale and the exact processing technology, the retorting process may be water and energy extensives. Oil shale has also been burnt directly as a low-grade fuel. A 2016 estimate by the World Energy Council set total world shale oil resources at 6.05 trillion barrels. The United States is believed to hold more than 80% of that total. There are around 600 known oil shale deposits around the world, including major deposits in the United States. Although oil shale deposits occur in many countries, only 33 countries possess known deposits of possible economic value. The largest deposits in the world occur in the United States in the Green River Formation, which covers portions of Colorado, Utah, and Wyoming. Approximately 70% of this resource lies on land owned or managed by the United States federal government. Well-explored deposits, potentially possessing additional economic value, include the Green River deposits in the western United States, the Tertiary deposits in Queensland, Australia, deposits in Sweden and Estonia, the El-Lajjun deposit in Jordan, and deposits in France, Germany, Brazil, Morocco, China, southern Mongolia and Russia. These deposits have given rise to expectations of yielding at least of shale oil per tonne of shale, using the Fischer Assay method. According to a survey conducted by the RAND Corporation, the cost of producing a barrel of oil at a surface retorting complex in the United States