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. Extracting the hydrocarbons from oil shale produces emissions and waste products that cause significant environmental concerns.
This is one reason why the world's extensive oil shale deposits have not been aggressively utilized. Shale core samples: When shale is drilled for oil, natural gas, or mineral resource evaluation, a core is often recovered from the well. The rock in the core can then be tested to learn about its potential and how the resource might be best developed. Shale is a rock composed mainly of clay-size mineral grains.
These tiny grains are usually clay minerals such as illite, kaolinite, and smectite. Shale usually contains other clay-size mineral particles such as quartz , chert , and feldspar. Other constituents might include organic particles, carbonate minerals, iron oxide minerals, sulfide minerals, and heavy mineral grains. These "other constituents" in the rock are often determined by the shale's environment of deposition, and they often determine the color of the rock.
Black shale: Organic-rich black shale. Natural gas and oil are sometimes trapped in the tiny pore spaces of this type of shale. Like most rocks, the color of shale is often determined by the presence of specific materials in minor amounts. Just a few percent of organic materials or iron can significantly alter the color of a rock. Shale gas plays: Since the late s, dozens of previously unproductive black organic shales have been successfully developed into valuable gas fields.
See the article: " What is Shale Gas? A black color in sedimentary rocks almost always indicates the presence of organic materials. Just one or two percent organic materials can impart a dark gray or black color to the rock. In addition, this black color almost always implies that the shale formed from sediment deposited in an oxygen-deficient environment.
Any oxygen that entered the environment quickly reacted with the decaying organic debris. If a large amount of oxygen was present, the organic debris would all have decayed. An oxygen-poor environment also provides the proper conditions for the formation of sulfide minerals such as pyrite , another important mineral found in most black shales. The presence of organic debris in black shales makes them the candidates for oil and gas generation.
If the organic material is preserved and properly heated after burial, oil and natural gas might be produced. The Barnett Shale, Marcellus Shale , Haynesville Shale , Fayetteville Shale , and other gas-producing rocks are all dark gray or black shales that yield natural gas. Gray shales sometimes contain a small amount of organic matter. However, gray shales can also be rocks that contain calcareous materials or simply clay minerals that result in a gray color.
Utica and Marcellus Shale: Two black organic shales in the Appalachian Basin are thought to contain enough natural gas to supply the United States for several years.
These are the Marcellus Shale and Utica Shale. Shales that are deposited in oxygen-rich environments often contain tiny particles of iron oxide or iron hydroxide minerals such as hematite , goethite, or limonite. Just a few percent of these minerals distributed through the rock can produce the red, brown, or yellow colors exhibited by many types of shale.
The presence of hematite can produce a red shale. The presence of limonite or goethite can produce a yellow or brown shale. Green shales are occasionally found. This should not be surprising because some of the clay minerals and micas that make up much of the volume of these rocks are typically a greenish color. Natural gas shale well: In less than ten years, shale has skyrocketed to prominence in the energy sector.
New drilling and well development methods such as hydraulic fracturing and horizontal drilling can tap the oil and natural gas trapped within the tight matrix of organic shales. Hydraulic properties are characteristics of a rock such as permeability and porosity that reflect its ability to hold and transmit fluids such as water, oil, or natural gas. Shale has a very small particle size, so the interstitial spaces are very small.
In fact they are so small that oil, natural gas, and water have difficulty moving through the rock. Shale can therefore serve as a cap rock for oil and natural gas traps, and it also is an aquiclude that blocks or limits the flow of groundwater. Although the interstitial spaces in a shale are very small, they can take up a significant volume of the rock. This allows the shale to hold significant amounts of water, gas, or oil but not be able to effectively transmit them because of the low permeability.
The oil and gas industry overcomes these limitations of shale by using horizontal drilling and hydraulic fracturing to create artificial porosity and permeability within the rock.
Oil and natural gas can migrate out of the shale, moving upwards where they are trapped within the pores of some other rock—such as sandstone. These deposits are known as conventional reservoirs since the fluid flows easily through the pores of the rock. Although drilling to extract oil and natural gas is possible, a large amount is still trapped inside the pore spaces of the shale. This oil and gas is difficult to remove, and it takes unconventional methods to access this oil and gas.
Pore spaces in shale are extremely tiny, and because of this gas cannot easily move out of the shale. However, some gas can be released through hydraulic fracturing , a method where water and chemicals are pumped down a well under pressure to fracture the shale. In addition, horizontal drilling was found to help with the release of natural gas trapped in shale. Oil shale is rock that contains large amounts of kerogen.
This type of shale forms when kerogen is buried at a depth of kilometers and can yield both liquid and gaseous hydrocarbons if the rock is heated or treated with solvents. Because of this the extensive oil shale deposits around the world are not actively used.
Fairly sophisticated investigation tools are used to determine the TOC content. Rock Eval pyrolysis is the most frequently used method which provides information about the content, origin and maturity of organic matter in the rock. The results are expressed as parameters S2, S3 and S4, respectively. The results are recalculated and expressed as the contents of pyrolisable, non-pyrolisable and total organic carbon TOC , as well as mineral carbon content.
In addition to TOC, pyrolytic analysis allows for the determination of other parameters that help to assess the type of organic matter, its thermal maturity and origin, alongside the properties that are used in oil and gas exploration.
The so-called maximum temperature, which indicates the stage of maturation of the organic matter, is an important parameter, along with hydrogen and oxygen indexes that characterize the type and origin of organic matter contained in the rock.
Potentially the most prospective oil and gas shale formations are located in Poland within three sedimentary basins: Baltic, Podlasie and Lublin Basin. TOC contents are highly variable in the Baltic Basin and range from 0. In the Podlasie Basin organic matter content range from low 0. I accept This website uses cookies. Organic matter content in shales. Organic matter content in shales Investigation of organic matter contained in the rock is a key stage of shale rock studies.
Polish shale gas in A summary. Shale gas resources - USA. There are several tens of prospective shale formations located in various US sedimentary basins. Level: madium. Shale gas resources - Europe. Geologists have identified within European basins a number of dark shale formations with a potential for shale gas accumulations.
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