Maceral
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Maceral
A maceral is a component, organic in origin, of coal or oil shale. The term 'maceral' in reference to coal is analogous to the use of the term 'mineral' in reference to igneous or metamorphic rocks. Examples of macerals are inertinite, vitrinite, and liptinite. Inertinite Inertinite is considered to be the equivalent of charcoal and degraded plant material. It is highly oxidised in nature and may be said to be burnt. A large portion of South Africa's coal reserves consist of inertinite. Vitrinite Vitrinite is shiny, glass-like material that is considered to be composed of cellular plant material such as roots, bark, plant stems and tree trunks. Vitrinite macerals when observed under the microscope show a boxlike, cellular structure, often with oblong voids and cavities which are likely the remains of plant stems. This has a high calorific value (24 - 28 MJ/kg) and a large proportion of volatile matter (24 - 30%). It often occurs interbanded or interlaminated with inertinit ...
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Funginite (maceral)
Funginite is a maceral, a component, organic in origin, of coal or oil shale, that exhibits several different physical properties and characteristics under particular conditions, and its dimensions are based upon its source and place of discovery. Furthermore, it is primarily part of a group of macerals that naturally occur in rocks containing mostly carbon constituents, specifically coal. Due to its nature, research into the chemical structure and formula of funginite is considered limited and lacking. According to Chen et al. referencing ICCP, 2001 (International Committee for Coal and Organic Petrology), alongside the maceral secretinite, they "are both macerals of the inertinite group, which is more commonly known as fossilized charcoal, and were previously jointly classified as the maceral sclerotinite". In the scientific community, the discernment between the two does not remain entirely clear, but there are slight particular and specific differences in regards to the compo ...
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Kerogen
Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It is insoluble in normal organic solvents and it does not have a specific chemical formula. Upon heating, kerogen converts in part to liquid and gaseous hydrocarbons. Petroleum and natural gas form from kerogen. Kerogen may be classified by its origin: lacustrine (e.g., algal), marine (e.g., planktonic), and terrestrial (e.g., pollen and spores). The name "kerogen" was introduced by the Scottish organic chemist Alexander Crum Brown in 1906,''Oxford English Dictionary'' 3rd Ed. (2003) derived from the Greek for "wax birth" (Greek: κηρός "wax" and -gen, γένεση "birth"). The increased production of hydrocarbons from shale has motivated a revival of research into the composition, structure, and properties of kerogen. Many studies have ...
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Vitrinite
Vitrinite is one of the primary components of coals and most sedimentary kerogens. Vitrinite is a type of maceral, where "macerals" are organic components of coal analogous to the "minerals" of rocks. Vitrinite has a shiny appearance resembling glass (vitreous). It is derived from the cell-wall material or woody tissue of the plants from which coal was formed. Chemically, it is composed of polymers, cellulose and lignin. The vitrinite group, which consists of various individual vitrinite ''macerals'', is the most common component of coals. It is also abundant in kerogens that are derived from the same biogenic precursors as coals, namely land plants and humic peats. Vitrinite forms diagenetically by the thermal alteration of lignin and cellulose in plant cell walls. It is therefore common in sedimentary rocks that are rich in organic matter, such as shales and marls with a terrigenous origin, or some terrigenous content. Conversely, carbonates, evaporites and well-sorted sandstone ...
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Cutinite
Cutinite is a liptinite maceral formed from terrestrial plant cuticles, and often found in coal deposits. It is classified as a Type II kerogen. References Coal Petrology {{petrology-stub Cutinite is a coal maceral of Liptinite In coal geology, liptinite is the finely-ground and macerated remains found in coal deposits. It replaced the term exinite as one of the four categories of kerogen. Liptinites were originally formed by spores, pollen, dinoflagellate cysts, leaf c ...
group of Macerals derived from waxy outer coating of leaves, roots, and stems. Cutinite is Hydrogen rich and it fluoresces under UV light. Reference: https://web.archive.org/web/20110720044325/http://mccoy.lib.siu.edu/projects/crelling2/atlas/macerals/mactut.html ...
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Inertinite
Inertinite is oxidized organic material or fossilized charcoal. It is found as tiny flakes within sedimentary rocks. The presence of inertinite is significant in the geological record, as it signifies that wildfires occurred at the time that the host sediment was deposited. It is also an indication of oxidation due to atmospheric exposure or fungal decomposition during deposition. Inertinite is a common maceral in most types of coal. The main inertinite submacerals are fusinite, semifusinite, micrinite, macrinite and funginite. The most common type of inertinite maceral is semifusinite. The optical properties of semifusinite are very similar to those of vitrinite. They differ in that semifusinite displays a folded texture as compared to vitrinite which generally maintains its composed structure. Inertinites also displays higher reflectance than vitrinite, except when approaching an anthracitic or graphite Graphite () is a crystalline form of the element carbon. It consists o ...
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Exinite
In coal geology, liptinite is the finely-ground and macerated remains found in coal deposits. It replaced the term exinite as one of the four categories of kerogen. Liptinites were originally formed by spores, pollen, dinoflagellate cysts, leaf cuticles, and plant resins and waxes.Taylor et al., 1998. Organic Petrography. Gebrüder Borntraeger, Berlin. pp. 176 M.C. Stopes introduced the term ''exinite'' in 1935 to describe the microscopic constituent of coal, rich in volatiles and relatively rich in hydrogen, that is represented by the exines of spores. C.A. Seyler in 1932, however, used the term with its present meaning, designating the following group of macerals: sporinite, cutinite, alginite (telalginite and lamalginite), resinite. Macerals A maceral is a component, organic in origin, of coal or oil shale. The term 'maceral' in reference to coal is analogous to the use of the term 'mineral' in reference to igneous or metamorphic rocks. Examples of macerals are inertinite ...
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Bituminite
Bituminite is an autochthonous maceral that is a part of the liptinite group in lignite, that occurs in petroleum source rocks originating from organic matter such as algae which has undergone alteration or degradation from natural processes such as burial . It occurs as fine-grained groundmass, laminae or elongated structures that appear as veinlets within horizontal sections of lignite and bituminous coals, and also occurs in sedimentary rocks. Its occurrence in sedimentary rocks is typically found surrounding alginite, and parallel along bedding planes. Bituminite is not considered to be bitumen because its properties are different from most bitumens. It is described to have no definite shape or form when present in bedding and can be identified using different kinds of visible and fluorescent lights. There are three types of bituminite: type I, type II and type III, of which type I is the most common. The presence of bituminite in oil shales, other oil source rocks and some coals ...
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Sporinite
Sporinite is a kind of exinite maceral found in coal formed from spores and pollen. It is a Type II kerogen Kerogen is solid, insoluble organic matter in sedimentary rocks. Comprising an estimated 1016 tons of carbon, it is the most abundant source of organic compounds on earth, exceeding the total organic content of living matter 10,000-fold. It .... References {{petrology-stub Coal Petrology ...
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Coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dead plant matter decays into peat and is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits of coal originate in former wetlands called coal forests that covered much of the Earth's tropical land areas during the late Carboniferous ( Pennsylvanian) and Permian times. Many significant coal deposits are younger than this and originate from the Mesozoic and Cenozoic eras. Coal is used primarily as a fuel. While coal has been known and used for thousands of years, its usage was limited until the Industrial Revolution. With the invention of the steam engine, coal consumption increased. In 2020, coal supplied about a quarter of the world's primary energy and over a third of its electricity. Some iron ...
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Coalbed Methane
Coalbed methane (CBM or coal-bed methane), coalbed gas, coal seam gas (CSG), or coal-mine methane (CMM) is a form of natural gas extracted from coal beds. In recent decades it has become an important source of energy in United States, Canada, Australia, and other countries. The term refers to methane absorbed into the solid matrix of the coal. It is called 'sweet gas' because of its lack of hydrogen sulfide. The presence of this gas is well known from its occurrence in underground coal mining, where it presents a serious safety risk. Coalbed methane is distinct from a typical sandstone or other conventional gas reservoir, as the methane is stored within the coal by a process called adsorption. The methane is in a near-liquid state, lining the inside of pores within the coal (called the matrix). The open fractures in the coal (called the cleats) can also contain free gas or can be saturated with water. Unlike much natural gas from conventional reservoirs, coalbed methane conta ...
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Lignite
Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat content. When removed from the ground, it contains a very high amount of moisture which partially explains its low carbon content. Lignite is mined all around the world and is used almost exclusively as a fuel for steam-electric power generation. The combustion of lignite produces less heat for the amount of carbon dioxide and sulfur released than other ranks of coal. As a result, environmental advocates have characterized lignite as the most harmful coal to human health. Depending on the source, various toxic heavy metals, including naturally occurring radioactive materials may be present in lignite which are left over in the coal fly ash produced from its combustion, further increasing health risks. Characteristics Lignite is brow ...
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Basin Modelling
Basin modelling is the term broadly applied to a group of geological disciplines that can be used to analyse the formation and evolution of sedimentary basins, often but not exclusively to aid evaluation of potential hydrocarbon reserves. At its most basic, a basin modelling exercise must assess: # The burial history of the basin (see back-stripping). # The thermal history of the basin (see thermal history modelling). # The maturity history of the source rock In petroleum geology, source rock is rock which has generated hydrocarbons or which could generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been depos ...s. # The expulsion, migration and trapping of hydrocarbons. By doing so, valuable inferences can be made about such matters as hydrocarbon generation and timing, maturity of potential source rocks and migration paths of expelled hydrocarbons. References * Duppenbecker S. J. ...
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