Oil Shale deposits are all over the world. These deposits were formed during the prehistoric periods of the Triassic, Jurassic, Permian, Devonian, Pre Cambrian, Cretaceous, Early Carboniferous, and Ordovician periods, which means that these deposits are very, very old. This is different from Oil Bearing Shale, which has much more “tight” oil.
Geologists look at Oil shale in order to find a substance called kerogen, which is a mixture of organic chemical organic compounds that are found in old organic matter. This very old organic matter is found in sedimentary rocks. In other words, animals and plants died, decomposed and broke down into kerogen over millennial time. The kerogen was then embedded in rocks that were formed underground and under great pressure.
As the photo shows, Oil Shale is finely grained and tough rock that needs to be heated up to about 700 degrees Fahrenheit, in order to extract the oil. There are two known ways to do this.
There is much interest in extracting oil from the vast oil shale deposits, but the processes may be so environmentally unsound or expensive that economic and environmental viability is in question.
The In Situ or Surface Retorting Method Of Extracting Oil And Gas From Oil Shale.
The first step is to drill a series of holes, about 600 feet deep, to reach the oil shale. This is done in a defined field that is about 30 by 20 feet in size. The holes are spaced about five feet apart in some procedures, with some holes at the perimeter and some in the central portion of the array.
The next step is to insert heating tubes that are capable of heating the oil shale to about 700 degrees, which liquefies the oil and releases the gas from the shale. This process can take from four months to several years!
Pumps at the surface suck the oil and gas up to ground level.
This is a photo of an Oil Shale Retort in Colorado.
Underground “Room and Pillar” Mining used along with above ground Retorting for oil extraction.
The oil shale is mined in a similar fashion to coal by digging out “rooms” and leaving underground supporting pillars. The oil shale is then transported to a facility where the Retorting Method can be done in above ground facilities. This method would have to include disposing of the spent oil shale and reclaiming the land where the mining has been completed.
A note about the Hydraulic Fracturing Method:
This is the controversial method is used to extract natural gas from oil shale. Hydraulic fracturing or “Frakking” is not used to extract oil from oil shale.
For more information about kerogen, shale oil deposits, and shale oil extraction, visit the following links:
Wikipedia “Kerogen” will give more information about this substance.
Wikipedia “Oil Shale Reserves” This link has charts that list the location the world’s shale oil reserves.
Google Images has many links to maps of the U.S. and other countries of the world. This map shows the general locations of the world’s oil shale reserves.
USShales has an excellent discussion of the In Situ and Room and Pillar extraction methods.
Wikipedia “Shale Oil Extraction” Has the most understandable explanation of the process.