Oil is one of the most versatile fossil fuels. Many products that people use everyday stem from petroleum. While most people know that that crude oiled is drilled for and pumped from conventional wells, not all oil comes from a well. Oil shale is a secondary source of oil that is present inside of rocks in a solid form instead of a liquid source. An oil similar to crude oil can be extracted from oil shale but the process of obtaining it is much more complex.
Oil shale
Similarly to oil, oil shale was formed from the deposits of organic and sediment material at the bottom of oceans and lakes. Over millions of years the material was changed by the heat and pressure, however, unlike normal oil, the process was never completed and the oil material was left stuck inside of sedimentary rocks. This material is called oil shale and the solid bituminous material is known as kerogen.
Also unlike oil, the oil shale must be mined, either at depth or by surface mining. Oil shale is found in deposits all over the world and the United States actually has the largest deposits which are found in areas of Colorado, Wyoming and Utah. Once the material has been recovered from the ground, it can then be processed to extract the kerogen as oil.
Extraction process
Once taken from the ground, the extracted oil shale can be refined using the process of pyrolysis. The pyrolysis process is the same process done to carbon material to form activated carbon and the material is heated to high temperatures in a low oxygen environment. The temperature involved is typically around 650 to 700 degrees Farenheit. At this temperature, the kerogen begins to melt inside the sedimentary rock. The melting kerogen can be separated from the surrounding rock and emerges as a substance similar to crude oil. With further refining, the removed kerogen can be turned into an imitation crude oil.
Development of the industry
While there are significant deposits of oil shale, few large commercial operations of extracting it for use have been applied. From a technical standpoint, the process has proven viable but with easier to obtain sources of oil available, there hasn’t been a move to begin large operation of extraction and refining oil shale.
There are also other concerns such as the environmental impact of the mining operations as well as the amount of water needed. In the United States, the oil shale deposits are located in an area that does not have significant water supplies and for each barrel of synthetic crude oil produced, several barrels of water are required. There is also the fact that the remaining rock will have to be dealt with as it still has residue of heavy metals and because of its pyrolysis activated, the rock volume has been increased so it can’t just go back into the hole it came from.
In-situ extraction
An alternative to the normal extraction process is the in-situ process which is being developed by the Shell Oil company. This process takes place in-situ, which means onsite, and does not involve removing the rock. Instead, holes are bored down to the deposit and heaters are used to heat the oil shale. Over the course of several years, the heat will create the same pyrolysis process and the kerogen can be separated for extraction onsite. This new method also comes with problems but as the price of oil continues to rise and the more available sources diminish, the deposits of oil shale could become of increasing value and importance to the areas that have them and can extract the oil.
