Molecular carbon isotopic evidence for the origin of geothermal hydrocarbons

Marais, David J. Des; Donchin, Jason H.; Nehring, N.L.; Truesdell, A.H.

doi:10.1038/292826a0

Cited by 222 publications

(111 citation statements)

References 7 publications

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“…This is consistent with experiments on gas generation from thermally mature organic matter (Lorant and Behar, 2002) and with observations of pyrobitumen in these reservoirs (Laughrey and Kostelnik, 2007 (Gherardi et al, 2005;Giggenbach, 1987). In systems where the concentrations of ethane and propane are abundant enough to allow isotopic analysis (Des Marais et al, 1981) partial reversals are observed. Recent work on Italian geothermal systems (Gherardi et al, 2005) shows one system with a normal 13 C sequence and two systems with d 13 C 1 > d 13 C 2 .…”

Section: Geochemical Processes 421 Ethane and Propane Destructionsupporting

confidence: 76%

“…Previous work described the origin of partial isotopic reversals by mixing between gases from different sources, including abiotic sources, and sources at different levels of thermal maturity (Jenden et al, 1993;Dai et al, 2004;Huang et al, 2004). Observations of partial reversals in gases from mineral exploration boreholes in 0146-6380/$ -see front matter Published by Elsevier Ltd. doi:10.1016/j.orggeochem.2010.09.008 crystalline Precambrian rocks (Sherwood Lollar et al, 2002, 2006 and in gases discharging from onshore and offshore geothermal systems (Des Marais et al, 1981;Proskurowski et al, 2008) has raised the possibility of an abiotic source from mineral catalyzed reduction of CO 2 with H 2 or polymerization of CH 4 (Sherwood Lollar et al, 2002. It is also known that oxidative destruction of hydrocarbon gases either microbially (James and Burns, 1984;Chung et al, 1988) or by thermochemical sulfate reduction (Krouse et al, 1988) can lead to partial reversals in isotopic composition.…”

Section: Introductionmentioning

confidence: 99%

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Carbon and hydrogen isotopic reversals in deep basin gas: Evidence for limits to the stability of hydrocarbons

Burruss

Laughrey

2010

Organic Geochemistry

268

139

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a b s t r a c tDuring studies of unconventional natural gas reservoirs of Silurian and Ordovician age in the northern Appalachian basin we observed complete reversal of the normal trend of carbon isotopic composition, such that d 13 C methane (C 1 ) >d 13C ethane (C 2 ) >d 13 C propane (C 3 ). In addition, we have observed isotopic reversals in the d 2 H in the deepest samples. Isotopic reversals cannot be explained by current models of hydrocarbon gas generation. Previous observations of partial isotopic reversals have been explained by mixing between gases from different sources and thermal maturities. We have constructed a model which, in addition to mixing, requires Rayleigh fractionation of C 2 and C 3 to cause enrichment in 13 C and create reversals. In the deepest samples, the normal trend of increasing enrichment of 13 C and 2 H in methane with increasing depth reverses and 2 H becomes depleted as 13 C becomes enriched. We propose that the reactions that drive Rayleigh fractionation of C 2 and C 3 involve redox reactions with transition metals and water at late stages of catagenesis at temperatures on the order of 250-300°C. Published ab initio calculated fractionation factors for C-C bond breaking in ethane at these temperatures are consistent with our observations. The reversed trend in d 2 H in methane appears to be caused by isotopic exchange with formation water at the same temperatures. Our interpretation that Rayleigh fractionation during redox reactions is causing isotopic reversals has important implications for natural gas resources in deeply buried sedimentary basins.Published by Elsevier Ltd.

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Section: Geochemical Processes 421 Ethane and Propane Destructionsupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Carbon and hydrogen isotopic reversals in deep basin gas: Evidence for limits to the stability of hydrocarbons

Burruss

Laughrey

2010

Organic Geochemistry

268

139

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“…Olefins are not stable over geologic time and are a reliable indicator for recent generation. In addition, higher amounts of ethene and propene in Leg 139 sediments are consistent with the results from other hydrothermal and geothermal settings, e.g., Whiticar and Suess (1990b) and DesMarais et al (1981). Drilling into resistant lithologies can also artificially generate higher hydrocarbons (bit metamorphism), including olefins Faber and Whiticar, 1989), but this is not considered likely in the sorbed-gas samples analyzed.…”

Section: Evidence Of Hydrothermal Activitysupporting

confidence: 71%

Thermogenic and Bacterial Hydrocarbon Gases (Free and Sorbed) in Middle Valley, Juan de Fuca Ridge, Leg 139

Whiticar¹,

Faber²,

Whelan³

et al. 1994

Proceedings of the Ocean Drilling Program, 139 Scientific Results

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The sorbed gases at all four Ocean Drilling Program Leg 139 sites (855, 856, 857, and 858) showed the unmistakable presence of thermogenic hydrocarbons. No indication of abiogenic gas was found. The evidence for the thermogenic hydrocarbons includes elevated contents of higher hydrocarbons (i.e., C λ l{C 2 + C 3 ] ca. 2-20), δ 13 C CH4 between -30‰ and -45‰ (PDB), 8 13 C C2 H 6 between -18.7‰ and -26. l‰, and δ 13 C c H from -20.5‰ to -25. l‰. The carbon isotope ratios of C 2 and C 3 indicate that the organic matter that generated these hydrocarbons is mature to overmature (1.8% to 4% Ro equivalent) reflecting the range in higher heat flow in the region. Considering the geologic setting, it is highly probable that the thermogenic gas was formed by hydrothermal processes. The presence of considerable amounts of ethene and propene (up to 7.1 hydrocarbon percent [h.c.%]) along with the accelerated maturation of organic matter support this conclusion. Some of the sorbed gases, especially at Sites 857 and 858, have a possible bacterial gas component admixed with the thermogenic, as is also seen in the free gases.The free gases are generally distinct from the sorbed gases and have C]/(C 2 + C 3 ) ratios up to 200 and δ 13 C CH as light as -56. l‰. The bacterial hydrocarbons in the free gas are most prominent at depths where bacterial sulfate reduction has removed most or all of the dissolved sulfate.It is uncertain from the geochemical information whether or not the hydrothermal gases are autothonous or have migrated into the sediments vertically or laterally. However, the general increase in hydrocarbon concentration with depth could indicate a limited upward diffusion or advection which is consistent with the heat and fluid flow information for these holes.

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“…Abiogenic hydrocarbons are interpreted to be derived from the polymerization of CH 4 units and give the reversed isotope distribution, in which 13 C 1 > 13 C 2 > δ 13 C 3 > δ 13 C 4 (Des Marais et al, 1981;Jenden et al, 1993a;Sherwood Lollar et al, 2002;2008). Such reversed isotope distribution is thought to be another distinct isotopic signature for abiogenically derived hydrocarbons.…”

Section: Discussion About the Origin Of Hydrocarbon Gases In Deep Laymentioning

confidence: 99%

“…However, abiogenic methane is frequently found in certain regimes such as oceanic mid-ridges, mud volcanoes and areas adjacent to abyssal fault zones (Abrajano et al, 1988;Charlou et al, 2002;Hosgormez et al, 2005). These abiogenic natural gases generally show a reversal pattern of carbon isotopic values for methane and their molecular homologues (i.e., 13 C 1 > 13 C 2 > 13 C 3 > 13 C 4 , Des Marais et al, 1981;Jenden et al, 1993a;Dai et al, 2005;Sherwood Lollar et al, 2002;2008). Abiogenic natural gases were thought forming by Fischer-Tropsch Synthesis (FTS) under subsurface ( Hu et al, 1998;Horita and Berndt, 1999;Sherwood Lollar et al, 2002Fiebig et al, 2007;Fu et al, 2007;Taran et al, 2007Taran et al, , 2010Proskurowski et al, 2008, Proskurowsk, 2010 or by water-rock interaction under the crust (Anderson et al, 1984;Douglas and Seyfried, 2004).…”

Section: Introductionmentioning

confidence: 99%

Fischer–Tropsch Synthesis Conducted in Volcanic Reservoir Stone, An Important Factor Caused a Reversed Pattern of Carbon Isotopic for Natural Gases Developed in Deep Layers, Songliao Basin North East China

Zhang

et al. 2013

Energy Exploration & Exploitation

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AbstractsTwo types of experiments of source rocks pyrolysis with volcanic reservoir rock and without one were conducted under hydrothermal condition and at 200 ˚C in gold tube system. The experiments result shows that there is a higher concentration of hydrocarbon gases generated in the experiment with rhyolite of reservoir stone and water than that with only water. Moreover, the hydrocarbon gases generated by experiments with rhyolite show a full reserved pattern of carbon isotope. This indicated that the FST reaction could happened between source rocks and volcanic reservoir rock at relatively low temperature.The numerical calculation for the carbon isotope of the gases from mixture between the gases from our FTS experiments and the typical organic hydrocarbon gases from deep layers of Songliao basin show that the contamination of a little FTS gas (<5% ,v/v) could cause the carbon isotope composition of thermal gases great variation. So, Fischer-Tropsch synthesis conducted in volcanic reservoir stone is an un-negligible factor caused the reversed pattern of carbon isotopic for natural gases developed in deep layers, Songliao Basin. This also indicated that the natural gases in deep layers of the basin are organic origin chiefly.

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Molecular carbon isotopic evidence for the origin of geothermal hydrocarbons

Cited by 222 publications

References 7 publications

Carbon and hydrogen isotopic reversals in deep basin gas: Evidence for limits to the stability of hydrocarbons

Carbon and hydrogen isotopic reversals in deep basin gas: Evidence for limits to the stability of hydrocarbons

Thermogenic and Bacterial Hydrocarbon Gases (Free and Sorbed) in Middle Valley, Juan de Fuca Ridge, Leg 139

Fischer–Tropsch Synthesis Conducted in Volcanic Reservoir Stone, An Important Factor Caused a Reversed Pattern of Carbon Isotopic for Natural Gases Developed in Deep Layers, Songliao Basin North East China

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