Significance of microbial processes in gases of the South Caspian basin

Katz, Barry J.; Narimanov, A. A.; Huseinzadeh, Rafiga

doi:10.1016/s0264-8172(02)00086-7

Cited by 60 publications

(32 citation statements)

References 12 publications

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“…10). Furthermore, the sub-vertical slope for the California gases in their plot is partly associated with the selective oxidation of propane, which leads to not only an increase of C 2 /C 3 but also to δ 13 C enrichment in the residual propane, thus to an increase in the difference of δ 13 C 2 -δ 13 C 3 (James and Burns, 1984;Katz et al, 2002). Although the trends observed in our experiments and those observed in the field by Prinzhofer and Huc (1995) are not completely consistent, they still have something in common, namely, the gas from kerogen cracking has larger C 2 /C 3 and smaller δ 13 C 2 -δ 13 C 3 whereas the oil cracking gas is characterized by smaller values of C 2 /C 3 and larger values of δ 13 C 2 -δ 13 C 3 .…”

Section: Discussionmentioning

confidence: 99%

“…5-7). Of course, microbial methane is also extremely depleted in 13 C, but the low content of methane (the C 1 /C 1-5 ratio by volume is less than 0.9) does not support the microbial process because the C 1 /C 1-5 ratio by volume for microbial gas is usually greater than 0.95 (Schoell, 1980;Katz et al, 2002). Accordingly, the TZ44a gas is most probably representative of kerogen gases in the Tazhong area.…”

Section: Natural Gas Plotmentioning

confidence: 99%

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Genetic origins of marine gases in the Tazhong area of the Tarim basin, NW China: Implications from the pyrolysis of marine kerogens and crude oil

Tian

Xiao

Wilkins

et al. 2010

International Journal of Coal Geology

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Section: Discussionmentioning

confidence: 99%

Section: Natural Gas Plotmentioning

confidence: 99%

Genetic origins of marine gases in the Tazhong area of the Tarim basin, NW China: Implications from the pyrolysis of marine kerogens and crude oil

Tian

Xiao

Wilkins

et al. 2010

International Journal of Coal Geology

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“…The researches on the hydrocarbon biodegradation reveals that the selective attack of gaseous hydrocarbons by bacteria will lead the rest hydrocarbon components become drier and their carbon isotopic compositions become notably heavier [13,14] . The content of the heavier hydrocarbons in the coalbed gas of the Xinji area is very low, showing that most of them have been decomposed.…”

Section: Analysis Of the Genetic Types Of Coalbed Gasmentioning

confidence: 99%

Secondary biogenic coalbed gas in some coal fields of China

et al. 2005

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The secondary biogenic coalbed gas, a new genetic and energy source type of coalbed gas in China, has been found in Xinji, Liyazhuang and Enhong areas. The essential characteristics of this type of gas are: (i) the major component of the gas is methane, with C 1 /C 1 5 value higher than 0.99, indicating that the gas is part of dry gas; (ii) the 13 C 1 value is in the range of 61.7‰ to 47.9‰, mostly lower than 55‰, which is much lower than the estimated 13 C 1 value of thermogenic methane according to the thermal evolution degree of the coal rocks (with R o value from 0.87% to 1.43%), showing the characteristics of the secondary biogenic gas; (iii) the D value of methane ranges from 244‰ to 196‰; (iv) 13 C 2 value ranges from 26.7‰ to 15.9‰ and 13 C 3 value ranges from 10.8‰ to 25.3‰, indicating that the heavier hydrocarbons have a thermogenic origin; (v) the content of CO 2 is very low, and 13 C CO2 value changes greatly, reflecting a characteristic of secondary change; (vi) 15 N 2 value ranges mainly from 1‰ to +1‰, indicating N 2 derived significantly from air. The negative linear correlation between the contents of N 2 and CH 4 reflects the activity of bacteria bearing surface water infiltrating into coal beds. The comprehensive tracing indices show that the coalbed gas in the studied areas is the mixed gas of primarily secondary biogenic gas and a part of remnant thermogenic gas. The uplift of coal beds and the development of faults in the studied areas create favorable conditions for the formation of the secondary biogenic gas.The coalbed gas refers to an in-situ generated and reservoired gas dominated by methane in coal beds, also called gas in the coalmine. Because of the great disaster caused by gas in coalmine production, the coalbed gas has been regarded as harmful gas for a long time. In 1980s, it was in America that the ground exploration and development of coalbed gas were first carried out successfully. This forms a new rising coalbed gas industry and proves that the coalbed gas could be recovered on a large scale on ground and used as a new and clean energy source as well as a high-quality chemical raw material. It is also believed that the coalbed gas is a non-conventional gas. As a result, the coalbed gas investigation has become a new branch of academic disciplines.The study of the genetic types of coalbed gas is one of the important researches . Generally, the coalbed gas can be divided into (microbial) biogenic gas and thermogenic gas [1 3] . Biogenic gas is formed through metabolic activities of bacteria at the early depositional stage of the organic matter, i.e. under thermal evolution degree of R o <0.5% or R o <0.3%, and its formation pathways include CO 2 reduction and acetate fermentation [4 6] . This kind of biogenic gas is called primary biogenic gas. The thermogenic coalbed gas is formed during coalification by the thermal degradation of hydrogen and oxygen rich functional groups with increasing temperatures.It is generally considered that it is very difficulty to preserve the prima...

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“…These characteristics correspond to moderate degrees of biodegradation using Peter and Moldowan's (1993) scale (level 4). In this case, microbial alteration of gases from the Guneshli field reported by Katz, Narimanov, and Huseinzadeh (2002) appears to occur at the same time interval with the oils. Stepwise decrease of n-alkanes in Fig.…”

Section: Biodegradationmentioning

confidence: 53%

Correlation, alteration, and origin of hydrocarbons in the GCA, Bahar, and Gum Adasi fields, western South Caspian Basin: geochemical and multivariate statistical assessments

Gürgey¹

2003

Marine and Petroleum Geology

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Significance of microbial processes in gases of the South Caspian basin

Cited by 60 publications

References 12 publications

Genetic origins of marine gases in the Tazhong area of the Tarim basin, NW China: Implications from the pyrolysis of marine kerogens and crude oil

Genetic origins of marine gases in the Tazhong area of the Tarim basin, NW China: Implications from the pyrolysis of marine kerogens and crude oil

Secondary biogenic coalbed gas in some coal fields of China

Correlation, alteration, and origin of hydrocarbons in the GCA, Bahar, and Gum Adasi fields, western South Caspian Basin: geochemical and multivariate statistical assessments

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