Oil and gas geochemistry and petroleum systems of the Fort Worth Basin

Hill, Ronald J.; Jarvie, Daniel M.; Zumberge, John E.; Henry, Mitchell E.; Pollastro, Richard M.

doi:10.1306/11030606014

Cited by 222 publications

(116 citation statements)

References 43 publications

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“…There are very few data in the literature on hydrogen gas concentrations in petroleum reservoirs. Hydrogen however, seems to be present below detection limits in most oilfield waters examined and is unlikely to represent more than 1 mol% (equivalent to 10 À2 atm) in associated gases (Hill et al, 2007). This again is compatible with the hydrocarbon oxidation pathways examined here ( Figure 9).…”

Section: Thermodynamic Constraints J Dolfing Et Alsupporting

confidence: 84%

Thermodynamic constraints on methanogenic crude oil biodegradation

2007

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Methanogenic degradation of crude oil hydrocarbons is an important process in subsurface petroleum reservoirs and anoxic environments contaminated with petroleum. There are several possible routes whereby hydrocarbons may be converted to methane: (i) complete oxidation of alkanes to H 2 and CO 2 , linked to methanogenesis from CO 2 reduction; (ii) oxidation of alkanes to acetate and H 2 , linked to acetoclastic methanogenesis and CO 2 reduction; (iii) oxidation of alkanes to acetate and H 2 , linked to syntrophic acetate oxidation and methanogenesis from CO 2 reduction; (iv) oxidation of alkanes to acetate alone, linked to acetoclastic methanogenesis and (v) oxidation of alkanes to acetate alone, linked to syntrophic acetate oxidation and methanogenesis from CO 2 reduction. We have developed the concept of a 'window of opportunity' to evaluate the range of conditions under which each route is thermodynamically feasible. On this basis the largest window of opportunity is presented by the oxidation of alkanes to acetate alone, linked to acetoclastic methanogenesis. This contradicts field-based evidence that indicates that in petroleum rich environments acetoclastic methanogenesis is inhibited and that methanogenic CO 2 reduction is the predominant methanogenic process. Our analysis demonstrates that under those biological constraints oxidation of alkanes to acetate and H 2 , linked to syntrophic acetate oxidation and methanogenesis from CO 2 reduction offers a greater window of opportunity than complete oxidation of alkanes to H 2 and CO 2 linked to methanogenic CO 2 reduction, and hence is the process most likely to occur.

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Section: Thermodynamic Constraints J Dolfing Et Alsupporting

confidence: 84%

Thermodynamic constraints on methanogenic crude oil biodegradation

2007

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“…Shale gas with typical positive carbon isotope sequence (a) and shale gas with typical reversed carbon isotope sequence (b). (Shale gas data of North America from Hill et al, 2007;Osborn and McIntosh, 2010;Zumberge et al, 2012;Rodriguez and Philip, 2010;Tilley and Muehlenbachs, 2013. Similarly hereinafter).…”

Section: Characteristics Of Light Hydrocarbon In Shale Gasmentioning

confidence: 99%

Geochemical Characteristics of Shale Gas in Xiasiwan Area, Ordos Basin

Dong

et al. 2015

Energy Exploration & Exploitation

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Well head gas samples from nine shale gas wells in Xiasiwan area were collected to examine their geochemical characteristics through analyzing their composition, carbon and hydrogen isotopes, and light hydrocarbon. The study shows the shale gas from Yanchang Formation is wet gas from primary cracking of sapropelic kerogen, and the shale system, still a closed system, has expelled only small amount of gas, and thermal maturity is the paramount factor restricting shale gas exploration; the shale gas from Shanxi Formation is dry coal-derived gas from secondary cracking, characterized by isotope reversal and δ 13 C 2 of less than -29‰, which proves that the ethane's carbon isotope of coalderived gas can be very low in high or over mature stage. A similar isotope "rollover" phenomenon in shale gas has also been observed in conventional gas of the Ordos Basin, so it is concluded that the gas in Lower Paleozoic is coalderived gas and the 13 C light ethane is the result of secondary cracking instead of mixing with oil-associated gas. Analysis of some indexes (such as δ 13 C 1 , δ 13 C 2 -δ 13 C 1 and light hydrocarbon) shows that the recoverable resources of shale gas in the mature stage are overestimated.

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“…Methane (CH 4 ) sourced from thermogenesis and/or biogenesis of organisms is the dominant component of shale gas (Hill et al, 2007;Strapoc et al, 2010;Zhang et al, 2012). The adsorption state is one of the most important forms of CH 4 in shale, and the content of adsorbed gases is up to 20-85% of total gases (Curtis, 2002;Jing et al, 2011;Montgomery et al, 2005).…”

Section: Introductionmentioning

confidence: 99%