Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Anne Marie Helmenstine, Ph. Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels.
Facebook Facebook Twitter Twitter. Updated August 02, Key Takeaways: Shale Shale is the most common sedimentary rock, accounting for about 70 percent of the rock in the Earth's crust.
Shale is a fine-grained rock made from compacted mud and clay. The defining characteristic of shale is its ability to break into layers or fissility. Black and gray shale are common, but the rock can occur in any color. Shale is commercially important. It is used to make brick, pottery, tile, and Portland cement. Natural gas and petroleum may be extracted from oil shale. Featured Video.
Cite this Article Format. Helmenstine, Anne Marie, Ph. Key Facts to Know about Shale Rock. Get to Know 24 Types of Sedimentary Rock. Slate Rock Definition, Composition, and Uses. One technology used for in situ oil extraction is known as volumetric heating. In this process, the rock is heated directly with an electric current. The heating element is injected either directly in a horizontal well or into a fractured area of the rock, until the oil shale begins producing shale oil. The oil could then be pumped directly from underground.
The internal combustion process uses a combination of gas, steam and spent shale produced by ex situ processing. These compounds are burned for pyrolysis. The hot gas is continually cycled through the oil shale, pyrolyzing the rock and releasing oil. Unfortunately, substances in the oil shale, such as sulfides, react with water to form toxic compounds that are harmful to the environment and to us.
Sulfides can cause effects from eye irritation to suffocation. Water containing toxic substances is unusable, and expensive to decontaminate. The process also produces heaps of ash. This ash can pollute ground, air, and water sources.
Another method that can be used either in situ or ex situ involves chemically reactive fluids. The fluids are injected directly into the retort zone where the rock is being heated. High-pressure hydrogen is one of the most common chemically reactive fluids.
It simultaneously heats the rock, removes sulfur, and upgrades the quality of the extracted oil. When shale oil is combusted heated , it releases carbon dioxide into the atmosphere. Carbon on the earth is contained in plants, soil, fossil fuels, and all living things—including us! The carbon in fossil fuels including coal, petroleum, natural gas, and oil shale has been sequester ed, or stored, underground for millions of years.
Burning fossil fuels releases carbon into the atmosphere at a much quicker rate than the trees, water, and ground can reabsorb it. Sometimes, climates can rise faster than organisms can adapt. Another environmental disadvantage to extracting shale oil is the enormous amounts of freshwater required. Water is necessary for drilling, mining, refining, and generating power. Some experts estimate that three litres. Some of this water is contaminated by toxic compounds, and is costly to decontaminate.
Mining can also contaminate groundwater. During in situ processing, toxic byproducts are left underground. They can leach into other sources of water, making them unsafe for drinking, hygiene , or development.
The United States has enormous proven deposits of oil shale. A source of oil in the United States would reduce the need for importing oil from other countries. This would put people to work and make the U. However, not all of oil shale is recoverable. This determines whether they are economically worth recovering. They have fewer impurities and are less complex than the carbonate-based oil shales in the Western United States, and thus cost less to extract and process.
Depositional history also matters: Oil shales that developed in wetlands or small lakes are very rich in energy. However, these formations are usually small. Larger lakes created larger shale formations, although these usually yield less oil. The process of extracting shale oil is expensive, much more expensive than the process of extracting crude oil. Due to this expense, the use of shale oil in the U. Companies have only mined for oil shale when the price of crude oil is high.
Today, the price of oil is relatively high and extraction technology is becoming more efficient and less expensive. The possibility of mining oil shale has again become a possibility. Communities, governments, oil companies, and environmental organizations must weigh the cost of extraction with the benefits of an oil resource. Oil shale is a lot like coal—they're both rocks that can be burned for energy.
Photograph by Emory Kristof. Some carbonate-rich shale deposits are also dinosaur-rich rock formations. The Irati Formation, in the state of Parana, Brazil, is a thin deposit of carbonate-rich shale.
It also contains many fossils of mesosaurs, a type of aquatic dinosaur. Silica Gems. In addition to oil shales, silica from ancient organisms created rock formations that are rich in minerals such as quartz, chert, and opal. Bakken formation. Fossil fuels formed from the remains of ancient plants and animals. Also called crude oil. Also called oil-shale oil and kerogen oil. Media Credits The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit.
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Related Resources. Managing Resources. View Collection. Energy Resources. Distribution of Natural Resources. Extracting Gas from Shale. View Activity. Conventional Oil and Natural Gas Reservoir: This drawing illustrates an "anticlinal trap" that contains oil and natural gas.
The gray rock units are impermeable shale. Oil and natural gas forms within these shale units and then migrates upwards. Some of the oil and gas becomes trapped in the yellow sandstone to form an oil and gas reservoir.
This is a "conventional" reservoir - meaning that the oil and gas can flow through the pore space of the sandstone and be produced from the well.
Black organic shales are the source rock for many of the world's most important oil and natural gas deposits. These shales obtain their black color from tiny particles of organic matter that were deposited with the mud from which the shale formed. As the mud was buried and warmed within the earth, some of the organic material was transformed into oil and natural gas.
The oil and natural gas migrated out of the shale and upwards through the sediment mass because of their low density. The oil and gas were often trapped within the pore spaces of an overlying rock unit such as a sandstone see illustration.
These types of oil and gas deposits are known as "conventional reservoirs" because the fluids can easily flow through the pores of the rock and into the extraction well. Although drilling can extract large amounts of oil and natural gas from the reservoir rock, much of it remains trapped within the shale. This oil and gas is very difficult to remove because it is trapped within tiny pore spaces or adsorbed onto clay mineral particles that make up the shale.
Unconventional Oil and Gas Reservoir: This drawing illustrates the new technologies that enable the development of unconventional oil and natural gas fields. In these gas fields, the oil and gas are held in shales or another rock unit that is impermeable.
To produce that oil or gas, special technologies are needed. One is horizontal drilling , in which a vertical well is deviated to horizontal so that it will penetrate a long distance of reservoir rock. The second is hydraulic fracturing. With this technique, a portion of the well is sealed off and water is pumped in to produce a pressure that is high enough to fracture the surrounding rock.
The result is a highly fractured reservoir penetrated by a long length of well bore. In the late s, natural gas drilling companies developed new methods for liberating oil and natural gas that is trapped within the tiny pore spaces of shale. This discovery was significant because it unlocked some of the largest natural gas deposits in the world. The Barnett Shale of Texas was the first major natural gas field developed in a shale reservoir rock.
Producing gas from the Barnett Shale was a challenge. The pore spaces in shale are so tiny that the gas has difficulty moving through the shale and into the well. Drillers discovered that they could increase the permeability of the shale by pumping water down the well under pressure that was high enough to fracture the shale.
These fractures liberated some of the gas from the pore spaces and allowed that gas to flow to the well. This technique is known as " hydraulic fracturing " or "hydrofracing. Drillers also learned how to drill down to the level of the shale and turn the well 90 degrees to drill horizontally through the shale rock unit. This produced a well with a very long "pay zone" through the reservoir rock see illustration. This method is known as " horizontal drilling. Horizontal drilling and hydraulic fracturing revolutionized drilling technology and paved the way for developing several giant natural gas fields.
These enormous shale reservoirs hold enough natural gas to serve all of the United States' needs for twenty years or more. Shale in brick and tile: Shale is used as a raw material for making many types of brick, tile, pipe, pottery, and other manufactured products. Brick and tile are some of the most extensively used and highly desired materials for building homes, walls, streets, and commercial structures.
Everyone has contact with products made from shale. If you live in a brick house, drive on a brick road, live in a house with a tile roof, or keep plants in "terra cotta" pots, you have daily contact with items that were probably made from shale.
Many years ago these same items were made from natural clay. However, heavy use depleted most of the small clay deposits. Needing a new source of raw materials, manufacturers soon discovered that mixing finely ground shale with water would produce a clay that often had similar or superior properties.
Today, most items that were once produced from natural clay have been replaced by almost identical items made from clay manufactured by mixing finely ground shale with water. The best way to learn about rocks is to have specimens available for testing and examination. Cement is another common material that is often made with shale. To make cement, crushed limestone and shale are heated to a temperature that is high enough to evaporate off all water and break down the limestone into calcium oxide and carbon dioxide.
The carbon dioxide is lost as an emission, but the calcium oxide combined with the heated shale makes a powder that will harden if mixed with water and allowed to dry. Cement is used to make concrete and many other products for the construction industry. Oil shale: A rock that contains a significant amount of organic material in the form of solid kerogen.
This specimen is approximately four inches ten centimeters across. Oil shale is a rock that contains significant amounts of organic material in the form of kerogen. This is usually much less efficient than drilling rocks that will yield oil or gas directly into a well.
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