GC: n

CT: Shale oil and natural gas resources are found in shale formations that contain significant accumulations of natural gas and/or oil. The Barnett Shale in Texas has been producing natural gas for more than a decade. Information gained from developing the Barnett Shale provided the initial technology template for developing other shale plays in the United States. Another important shale gas play is the Marcellus Shale in the eastern United States. While the Barnett and Marcellus formations are well-known shale gas plays in the United States, more than 30 U.S. states overlie shale formations.
Within an individual shale play, geophysicists and geologists identify suitable well locations in areas that have the greatest potential to produce commercial volumes of natural gas and oil. These areas are identified using rock core samples and geophysical and seismic technologies to generate maps of the subsurface hydrocarbon resources in a shale formation.

S: https://www.eia.gov/energy_in_brief/article/shale_in_the_united_states.cfm (last access: 29 December 2016)

N: 1. shale (n): Possibly a specialized use of Middle English schale (shell, husk, pod) in the late 14c.
oil (n): First meant exclusively olive oil from Anglo-French and Old North French olie till c. 1300, but in 1520 it was recorded to mean “petroleum”. However, it was not common until 19c.
2. A type of unconventional oil found in shale formations.
3. A type of petroleum that is produced or obtained through techniques other than traditional oil well extraction. Unconventional oil production is commonly seen as more costly than conventional oil production, less efficient, and is likely to cause more environmental damage. This is because unconventional oil is considered “heavier” and requires more complex procedures to process.
4. Oil shale was formed millions of years ago by deposition of silt and organic debris on lake beds and sea bottoms. Over long periods of time, heat and pressure transformed the materials into oil shale in a process similar to the process that forms oil; however, the heat and pressure were not as great. Oil shale generally contains enough oil that it will burn without any additional processing, and it is known as “the rock that burns”. Oil shale can be mined and processed to generate oil similar to oil pumped from conventional oil wells; however, extracting oil from oil shale is more complex than conventional oil recovery and currently is more expensive.
5. 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.
6. Relatively high prices for conventional oil in the 1970s and 1980s stimulated interest and some development of better oil shale technology, but oil prices eventually fell, and major research and development activities largely ceased.

S: 1. OED – http://www.etymonline.com/index.php?term=oil&allowed_in_frame=0 (last access: 13 December 2016). 2 & 3. IVT – http://www.investopedia.com/terms/s/shaleoil.asp (last access: 13 December 2016) 4 to 6. OSTSEIS – http://ostseis.anl.gov/guide/oilshale/ (last access: 19 December 2016).

SYN:
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CR: natural gas, petroleum, pyrolysis, shale gas.