Petrographic changes induced by artificial coalification of peat: comparison of two planar facies (Rhizophora and Cladium) from the Everglades-mangrove complex of Florida and a domed facies (Cyrilla) from the Okefenokee Swamp of Georgia

Cohen, Arthur D.; Bailey, Alan M.

doi:10.1016/s0166-5162(97)00022-0

Cited by 28 publications

(11 citation statements)

References 29 publications

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“…Both exsudatinite and the oil droplets are associated with resinite and/or suberinite. This is consistent with early petroleum generation from resinite at VR values of 0.4 to 0.6%R o , a feature that has been confirmed by artificial maturation of resinite and resin-containing peat (Snowdon and Powell, 1982;Shanmugam, 1985;Khavari Khorasani, 1987;Lewan and Williams, 1987;Stout, 1995;Cohen and Bailey, 1997). Similarly, suberinite has been shown to be thermally unstable at low maturities Khavari Khorasani, 1990, 1995).…”

Section: Petroleum Generation and The Oil Windowsupporting

confidence: 69%

Petroleum Potential, Thermal Maturity and the Oil Window of Oil Shales and Coals in Cenozoic Rift Basins, Central and Northern Thailand

Petersen

Foopatthanakamol

Ratanasthien

2006

Journal of Petroleum Geology

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Oil shales and coals occur in Cenozoic rift basins in central and northern Thailand. Thermally immature outcrops of these rocks may constitute analogues for source rocks which have generated oil in several of these rift basins. A total of 56 oil shale and coal samples were collected from eight different basins and analysed in detail in this study. The samples were analysed for their content of total organic carbon (TOC) and elemental composition. Source rock quality was determined by Rock‐Eval pyrolysis. Reflected light microscopy was used to analyse the organic matter (maceral) composition of the rocks, and the thermal maturity was determined by vitrinite reflectance (VR) measurements. In addition to the 56 samples, VR measurements were carried out in three wells from two oil‐producing basins and VR gradients were constructed. Rock‐Eval screening data from one of the wells is also presented. The oil shales were deposited in freshwater (to brackish) lakes with a high preservation potential (TOC contents up to 44.18 wt%). They contain abundant lamalginite and principally algal‐derived fluorescing amorphous organic matter followed by liptodetrinite and telalginite (Botryococcus‐type). Huminite may be present in subordinate amounts. The coals are completely dominated by huminite and were formed in freshwater mires. VR values from 0.38 to 0.47%Ro show that the exposed coals are thermally immature. VR values from the associated oil shales are suppressed by 0.11 to 0.28%Ro. The oil shales have H/C ratios >1.43, and Hydrogen Index (HI) values are generally >400 mg HC/g TOC and may reach 704 mg HC/ gTOC. In general, the coals have H/C ratios between about 0.80 and 0.90, and the HI values vary considerably from approximately 50 to 300 mg HC/gTOC. The HImax of the coals, which represent the true source rock potential, range from ∼160 to 310 mg HC/g TOC indicating a potential for oil/gas and oil generation. The steep VR curves from the oil‐producing basins reflect high geothermal gradients of ∼62°C/km and ∼92°C/km. The depth to the top oil window for the oil shales at a VR of ∼0.70%Ro is determined to be between ∼1100 m and 1800 m depending on the geothermal gradient. The kerogen composition of the oil shales and the high geothermal gradients result in narrow oil windows, possibly spanning only ∼300 to 400 m in the warmest basins. The effective oil window of the coals is estimated to start from ∼0.82 to 0.98%Ro and burial depths of ∼1300 to 1400 m (∼92°C/km) and ∼2100 to 2300 m (∼62°C/km) are necessary for efficient oil expulsion to occur.

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Section: Petroleum Generation and The Oil Windowsupporting

confidence: 69%

Petroleum Potential, Thermal Maturity and the Oil Window of Oil Shales and Coals in Cenozoic Rift Basins, Central and Northern Thailand

Petersen

Foopatthanakamol

Ratanasthien

2006

Journal of Petroleum Geology

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“…Additional studies deal with aspects of the chemistry that occur during early stages of the coalification processes. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] The chemical transformations of organic oxygen functionalities are an integral part of this process. Thermal chemistry and other pathways contribute to the alterations of the deposited materials that are the precursors of coals.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Organically Bound Oxygen Forms in Lignites, Peats, and Pyrolyzed Peats by X-ray Photoelectron Spectroscopy (XPS) and Solid-State ¹³C NMR Methods

et al. 2002

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A combination of XPS and solid-state 13C NMR techniques have been used to characterize organic oxygen species and carbon chemical/structural features in peats, pyrolyzed peats, lignites, and other coals. Both the 13C NMR and XPS results show the same ordering for the amount of aromatic carbon, higher ranking coals > lignites > peats. In general the value for H/C decreases as the percent of aromatic carbon increases. For pyrolyzed peats, the H/C level is higher than lignites and other coals of comparable levels of aromatic carbon. This is likely due to significant differences in the carbon structural framework of these materials. A van Krevelen plot, based on elemental H/C data and XPS derived O/C data, shows the well-established pattern for peats, lignites, and other coals. In general, O/C decreases as the percent of aromatic carbon increases, with the expected magnitude ordering, peats > lignites > higher ranking coals. Most of the H/C values of pyrolyzed peats are higher than coals at comparable O/C. A range of O/C levels (0.23−0.13) were produced from pyrolysis of peats; however, these data, when plotted versus the percent aromatic carbon, fall below the values for lignites and other coals. These results indicate that simple pyrolysis does not appear to fully capture the chemical transformations encountered during the natural formation of coals. Both XPS and 13C NMR results are sensitive to the basic difference in the kinds of organic oxygen species found in peats and coals. The advantages of using a combination of XPS and 13C NMR along with the pitfalls of using a single technique for organic oxygen speciation are discussed. For peats, pyrolyzed peats, lignites, and other coals, XPS results for the total amount of organic oxygen fall between upper and lower limit estimates based on 13C NMR derived parameters associated with different oxygen species. For lignites and other coals, there is a sharp drop in the number of carbonyl and carboxyl groups near 60% aromatic carbon. The amount of carbon− oxygen single-bonded species reflected in the NMR parameters falO and faOCH3 and the XPS parameter C−O oxygen, decrease as the percent aromatic carbon increases. The highest levels of phenolic and phenoxy oxygen are found near 60% aromatic carbon. NMR results show that the amount of phenolic and phenoxy carbon (faP) and aliphatic carbon−oxygen single-bonded species (falO) are very similar for pyrolyzed peats, lignites, and other coals at comparable levels of aromatic carbon. These results indicate that thermal decarboxylation/decarbonylation and demethoxylation pathways exist for peat and suggest that similar pathways occur during natural coalification processes.

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“…This was based on the fact that modern peat deposits often have abundant plant phytoliths and other biogenic inorganic material (e.g. Cohen and Bailey, 1997) but these constituents are very rare in coal deposits and commonly comprise less than 2% of the inorganic fraction, e.g. in Miocene coals from Costa Rica (Sanchez et al, 1987).…”

Section: Discussionmentioning

confidence: 99%

“…Of these few studies, most focused on characterizing changes in geochemical composition, organic compounds and their concentrations, e.g. increasing aromatic character and C content, decreasing O and H contents (Stach et al, 1982;Orem et al, 1996), as well as petrographic changes (Hayatsu et al, 1984;Rollins et al, 1991;Cohen and Bailey, 1997). Only a few previous studies have documented the chemical changes to the inorganic fraction during artificial coalification (Rollins et al, 1991;Willis et al, 1991;Bailey and Cohen, 1993).…”

Section: Introductionmentioning

confidence: 99%

Neo-mineral formation during artificial coalification of low-ash — mineral free-peat material from tropical Malaysia-potential explanation for low ash coals

Wüst

Bustin

Ross

2008

International Journal of Coal Geology

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Petrographic changes induced by artificial coalification of peat: comparison of two planar facies (Rhizophora and Cladium) from the Everglades-mangrove complex of Florida and a domed facies (Cyrilla) from the Okefenokee Swamp of Georgia

Cited by 28 publications

References 29 publications

Petroleum Potential, Thermal Maturity and the Oil Window of Oil Shales and Coals in Cenozoic Rift Basins, Central and Northern Thailand

Petroleum Potential, Thermal Maturity and the Oil Window of Oil Shales and Coals in Cenozoic Rift Basins, Central and Northern Thailand

Characterization of Organically Bound Oxygen Forms in Lignites, Peats, and Pyrolyzed Peats by X-ray Photoelectron Spectroscopy (XPS) and Solid-State ¹³C NMR Methods

Neo-mineral formation during artificial coalification of low-ash — mineral free-peat material from tropical Malaysia-potential explanation for low ash coals

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Petrographic changes induced by artificial coalification of peat: comparison of two planar facies (Rhizophora and Cladium) from the Everglades-mangrove complex of Florida and a domed facies (Cyrilla) from the Okefenokee Swamp of Georgia

Cited by 28 publications

References 29 publications

Petroleum Potential, Thermal Maturity and the Oil Window of Oil Shales and Coals in Cenozoic Rift Basins, Central and Northern Thailand

Petroleum Potential, Thermal Maturity and the Oil Window of Oil Shales and Coals in Cenozoic Rift Basins, Central and Northern Thailand

Characterization of Organically Bound Oxygen Forms in Lignites, Peats, and Pyrolyzed Peats by X-ray Photoelectron Spectroscopy (XPS) and Solid-State 13C NMR Methods

Neo-mineral formation during artificial coalification of low-ash — mineral free-peat material from tropical Malaysia-potential explanation for low ash coals

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Product

Resources

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Characterization of Organically Bound Oxygen Forms in Lignites, Peats, and Pyrolyzed Peats by X-ray Photoelectron Spectroscopy (XPS) and Solid-State ¹³C NMR Methods