If vitrinite reflectance data are available, the relationship between transformation ratio and maturity can be used to predict (1) percentage of kerogen that has generated hydrocarbons at a given depth and (2) hydrocarbon yields. Nakamura, T. (2005) "Post-hydration thermal metamorphism of carbonaceous chondrites". This classification was developed originally for coal (a sedimentary rock that is rich in organic matter of terrestrial origin) but is now applied to the study of other kerogen-rich sedimentary deposits. These organic-walled microfossils have high H/C values because they formed hydrocarbons biologically. And yet, kerogen’s basic internal structure has remained poorly understood — until now. Kerogen type IV is composed of hydrogen-poor constituents such as inertinite, which is detrital organic matter oxidized directly by thermal maturation including fire (charcoal) or by biological or sedimentological recycling. For example, kerogen from the Green River Formation oil shale deposit of western North America contains elements in the proportions carbon 215 : hydrogen 330 : oxygen 12 : nitrogen 5 : sulfur 1.[11]. [29][30][31] This evolution is consistent with the change in carbon speciation from predominantly aliphatic (similar to wax, density < 1 g/ml) to predominantly aromatic (similar to graphite, density > 2 g/ml) with increasing thermal maturity. [20][21] These results can be explained by the preferential removal of aliphatic carbons by cracking reactions during pyrolysis, where the cracking typically occurs at weak C-C bonds beta to aromatic rings and results in the replacement of a long aliphatic chain with a methyl group. Diagenesis Francis, 2014 - There is a range of kerogen types, reflecting the type of original organic matter and the environment of deposition. organic. The type of material is difficult to determine but several apparent patterns have been noticed. 2 assesses these conclusions). Dembicki, H., B. Horsfield, and T. Y. Ho, 1983. These changes in composition and microstructure result in changes in the properties of kerogen. ... Organics to petroleum - zooplankton; 'sapropel'; fats, resinous, waxy. Resulting changes in the burial temperatures and pressures lead to further changes in kerogen composition including loss of hydrogen, oxygen, nitrogen, sulfur, and their associated functional groups, and subsequent isomerization and aromatization Such changes are indicative of the thermal maturity state of kerogen. This gives a direct indicator of the kerogen type and types of hydrocarbons that can be generated by the kerogen during the maturation process. Sapropelic kerogen is formed through Examples include spores and pollen of land plants, primarily marine phytoplankton cysts (acritarchs and dinoflagellates), and some land plant components such as leaf and stem cuticles. This page was last modified on 1 August 2016, at 12:46. The hydrocarbon generation-depth curve in Figure 1indicates where various phases of hydrocarbons would be generated today in the geologic section if a uniform kerogen existed throughout. The hydrogen content of kerogen is the controlling factor for oil vs. gas yields from the primary hydrocarbon-generating reactions. marine. ... clay types and maturation , kerogen type and maturation, permeability, porosity, and saturation. This breakdown process can be viewed as the reverse of photosynthesis. Types of Kerogen• Type I : algal kerogen – “best” oil source – Lipid-rich Lipid-• Type II: herbaceous II: kerogen – Good oil source – Includes zooplankton (sapropelic)• Type III: woody III: kerogen (coaly) – Good gas source 9. There are different types or classes of kerogen. Kerogen is the portion of naturally occurring organic matter that is nonextractable using organic solvents. I-1). [4] Variations in the mineral matrix effect related to organic richness occur in whole-rock samples with TOC values less than 10%.[4][5][7]. [7] These resulting units can then polycondense to form geopolymers. A large proportion of type I kerogen can be thermally converted to petroleum and therefore is rarely recognizable in thermally mature or postmature rocks. General composition of oil shales constitutes inorganic matrix, bitumens, and kerogen. Appraisal and development are the key value areas for Zennor Petroleum and Pandion Energy—two producers owned by oil and gas-focused private equity (PE) firm Kerogen Capital—as well as the driving logic for the company to invest in AIM-listed Hurricane Energy. Kerogen is a mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rocks. Type I kerogen – High initial H/C and low initial O/C ratios. Then transfer to the dept… Acknowledgments Kerogen type IV is a term not universally employed by organic geochemists because it is difficult to distinguish type IV from type III using only Rock-Eval pyrolysis. 21, 1981. 10th World Petroleum Congress (2) 12th World Petroleum Congress (2) ... is extracted by comparing experimental observations to the solution of diffusion equation in the domain of pore/kerogen interface. Type IV kerogen comprises mostly inert organic matter in the form of polycyclic aromatic hydrocarbons. These generated species are partially expelled from the kerogen-rich source rock and in some cases can charge into a reservoir rock. The original organic matter can comprise lacustrine and marine algae and plankton and terrestrial higher-order plants. Aromatization allows for molecular stacking in sheets, which in turn drives changes in physical characteristics of kerogen, such as increasing molecular density, vitrinite reflectance, and spore coloration (yellow to orange to brown to black with increasing depth/thermal maturity). On a mass basis, rocks containing type I kerogen yield the largest quantity of hydrocarbons upon pyrolysis. Different type of Kerogen produces different type of hydrocarbon (Table I-1 and Fig. Type III Kerogen. Often the organic matter is structureless (amorphous) alginite and, when immature, fluoresces golden yellow in ultraviolet (UV) light. When kerogen is contemporaneously deposited with geologic material, subsequent sedimentation and progressive burial or overburden provide elevated pressure and temperature owing to lithostatic and geothermal gradients in Earth's crust. Hence, from the theoretical view, shales containing type I kerogen are the most promising deposits in terms of conventional oil retorting.[34]. Closely related environments of deposition result in the same path. In its pure form, it is composed of vitrinite, a maceral formed from land plant wood. Structured kerogens include woody, herbaceous, vitrinite, and inertinite. Kerogen types ~ Learning Geology. Amorphous kerogens are by far the most prevalent and include most of the algal material. OIL FORMATION 10. Geological burial processes cause clays to undergo physical and chemical alteration usually preceding the slow and systematic thermal conversion (generation) of kerogen to petroleum. Three main types of kerogen can be recognized (Figures 6):-Type I kerogen. Kerogens are composed of a variety of organic materials, including algae, pollen, wood, vitrinite, and structureless material. Prauss, M., and W. Riegel, 1989, Evidence from phytoplankton associations for causes of black shale formation in epicontinental seas: Neues Jahrbuch fur Geologie und Palaontologie, Monatshefte, v. 11, p. 671-685. The types of kerogens present in a rock largely control the type of hydrocarbons generated in that rock. Thus, kerogen type is an indicator of depositional environment. There is also a Type IIs and a Type IV, but for the “non-geochemist” we will stop with the three main types. Generated by the most abundant fraction of organic matter preserved in the progressive of. Characterized by low initial H/C ratios and intermediate initial H/C ratios and intermediate initial and... 6 ] these concepts explain why kerogen is going to change into oil gas. 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