Research ArticleIsotopic Composition of Abiogenic Gas Produced inClosed-System Fischer-Tropsch Synthesis: Implications for theOrigins of the Deep Songliao Basin Gases in China
Zhifu Wei ,1 Yongli Wang ,2 Gen Wang ,1 Xueyun Ma,1,3 Wei He,1,3 Ting Zhang,1,3
Xiaoli Yu,1,3 and Yan-Rong Zou4
1Key Laboratory of Petroleum Resources Research, Gansu Province, Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences, Lanzhou 730000, China2Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences; CASCenter for Excellence in Life and Paleoenvironment, Beijing 100029, China3University of Chinese Academy of Sciences, Beijing 100049, China4The State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences,Guangzhou 510640, China
In this study, closed-system Fischer-Tropsch synthesis was conducted at 380°C and 30MPa for 72 h with magnetite as a catalyst.The isotopic composition of the closed-system Fischer-Tropsch synthesis gas and the composition of known abiogenic gas weresystematically studied, and the deep Songliao Basin gas was also investigated. The results show that closed-system Fischer-Tropsch synthesis of gaseous hydrocarbon isotopes exhibits a partial reverse order, which includes the reverse order of methaneand ethane such as δ13C-C1>δ13C-C2<δ13C-C3 and δ2H-C1>δ2H-C2<δ2H-C3. Furthermore, experimental data on the control ofNaBH4 content indicates that the carbon isotopes demonstrate a reverse order on condition that the H2/CO2 (mole ratio) isequal to or greater than 4.0; meanwhile, the hydrogen isotopes show a normal order. The deep Songliao Basin hydrocarbon gascomponent is similar to thermogenic gas and has a trend of a transition to oceanic hydrothermal system abiogenic gas. Inaddition, the deep Songliao Basin gas isotopic pattern is different from both Lost City and Kidd Creek where the deep Basin gascarbon isotopic pattern has a reverse order, and the hydrogen isotopic pattern has a normal order. Therefore, the deep Basin gasmight be a mixture of the oil-type gas and the coal-formed gas, which could be the cause of the isotopic reverse.
1. Introduction
Generally, hydrocarbons are mainly derived from microbialdecomposition of organic matter [1–3] and organic matterthermal degradation [2, 4]. However, abiogenic hydrocar-bons are produced by chemical reactions that do not directlyinvolve organic matter and are present in trace amounts inhigh-temperature volcanic/geothermal fluids and magmasystems [5–7]. The researchers found that a large proportionof abiotic hydrocarbons (up to 90 vol.%) associated withlow-temperature gas-water rock interactions were presentin Precambrian crystalline shield, submarine peridotite
hydrothermal system, continental ophiolite, and serpenti-nized ultramafic rocks in peridotite blocks [8–12]. Abiogenicgas associated with continental serpentinized ultramafic rocksystems have been found in many countries from NorthAmerica, Europe, and Asia to Oceania [8, 13–18]. Typicalcharacteristics of the gas include a high concentration ofmethane (CH4, usually greater than 80 vol. %), variableamounts of hydrogen (H2) and C2+ alkanes (ethane, propane,and butane), and typical combinations of stable C and H iso-topes of CH4, which overlap only partially with biological(thermal) gases [9, 19]. In fact, abiogenic gas is related to aprocess known as Fischer-Tropsch synthesis (FTS) [20–22].
HindawiGeofluidsVolume 2019, Article ID 2823803, 13 pageshttps://doi.org/10.1155/2019/2823803
Fischer-Tropsch synthesis (FTS) was first developed byGerman chemists Franz Fischer and Hans Tropsch in 1926,and it is a chemical process that converts carbon monoxidefrom coal into liquid hydrocarbon-based fuels and lubricants[23]. Usually, it can be defined as a heterogeneous catalyticreduction of carbon dioxide using molecular hydrogen,which is widely considered to be a process that may lead tothe presence of organic compounds in meteorites, subma-rine hydrothermal systems, and igneous rocks [24–29].Organic compounds produced by Fischer-Tropsch synthesis(FTS) are used to explain the existence of hydrocarbons inigneous rocks and hydrothermal fluids, and they areinvolved in a variety of geological processes, including theproduction of methane and hydrocarbons deep in the crust,which provides nutrients for microorganisms in under-ground and hydrothermal environments ([30]; Szamtmari,1989; [22, 27, 31–33]).
It has previously been observed that some abiogenic CO2and biogenic hydrocarbon gas reservoirs have been foundsuccessively in the Xujiaweizi fault depression of the SongliaoBasin [34, 35]. Most of these gases are produced by Ro >2 0% source rocks and have carbon isotopic reversals(δ13C − C1 > δ13C − C2; δ
13C − C2 > δ13C − C3) [36]. Theirgenetic origin has been debated for a long time (e.g., Guoet al. 1997; [37–41]), mainly because of their common carbonisotopic reversals. Previous studies have found that the deepnatural gas in the Songliao Basin is dominated by hydrocar-bon gas. The carbon isotope composition of methane is rela-tively heavy (>-30.0‰), and the carbon isotopic reversaltrend is general, so it is believed that there are abiogenicalkane gases in the Xujiaweizi fault depression, which is con-sidered to be related to mantle degassing ([42]; Guo et al.1997; [43, 44]). Others have argued that the mixing of differ-ent types of natural gas formed by organic matter in the sameformation is the main reason for those results [45]. In thisstudy, the experimental data and the isotopic compositionof abiogenic gas were systematically studied with closed-system Fischer-Tropsch synthesis and pyrolysis at 380°Cand 30MPa, and the deep Songliao Basin gas was also inves-tigated to provide more information for exploring thesources of the deep Songliao Basin gas.
2. Geological Setting
Songliao Basin is a complex faulted basin in which the LowerCretaceous is dominated by faulted sedimentation andcontains a natural gas reservoir, and the Upper Cretaceousis dominated by depression sedimentation and contains apetroleum reservoir [46]. The Xujiaweizi fault depressionis located in the north part of the Songliao Basin(Figure 1(a)). From younger to older, the deep strata ofthe Xujiaweizi fault depression comprise the DengloukuFormation, Yingcheng Formation, Shahezi Formation, andHuoshiling Formation (Figure 1(b)) [36]. Among these, thedeposition periods of the Huoshiling and Yingcheng forma-tions were the main developing times for volcanic rocks infault depression, the deposition period of Shahezi Formationwas the main developing period for hydrocarbon sourcerocks in the fault depressions, and the Denglouku Formation
was the regional cap rock of the natural gas in the deep faultdepression [41].
The Xujiaweizi fault depression mainly develops two setsof source rocks of the Lower Cretaceous Shahezi Formation(K1sh) and Yingcheng Formation (K1yc). The source rocksof Shahezi Formation are widely distributed, mainly in thecentral, western, and northern parts of the fault depression,with a thickness of more than 200m, whereas source rocksin the Yingcheng Formation are mainly distributed in theXuzhong area and the southern part of the fault depressionwith a maximum thickness of 160m. The TOC averagevalues of Shahezi Formation and Yingcheng Formation are2.43% and 1.41%, respectively [47]. The organic matter typesare mainly type III, and the vitrinite reflectance Ro averagevalues are 2.36% and 2.24%, respectively [47]. Both sets ofsource rocks are in stages of high to overmature evolution.The main deep gas reservoir types include the Dengloukustructural gas reservoir, Yingcheng Formation volcanic litho-logic gas reservoir and basement lithologic gas reservoir. TheXujiaweizi fault depression is the most abundant hydrocar-bon gas reservoir in volcanic rocks around the world [48]with proven gas reserves exceeding 250 billion cubic metersthat have been discovered since the milestone well XS1 wasdrilled in 2002. Gas fields, such as Wangjiatun, Songfangtun,Changde, Nongan, and Qingshen, have been discovered inthe Xujiaweizi fault depression and its surroundings.
3. Fischer-Tropsch Synthesis
Abiogenic synthesis of hydrocarbons has been discussedsince 1940 [49]. Many methods have been described, andalthough the researchers have not yet reached a conclusion,it is generally believed that hydrocarbons could be producedby reduction of CO2 via an aqueous Fischer-Tropsch synthe-sis (FTS) reaction. The Fischer-Tropsch reaction is a com-mon industrial process invented by German scientistsFranz Fischer and Hans Tropsch in the 1920s. The mass bal-ance equation is as follows:
2n + 1 H2 + nCO⟶ CnH2n+2 + nH2O 1
Although the first study of FTS began in the early 20thcentury, the mechanism of hydrocarbon formation fromCO and H2 is still controversial because the whole processis a very complex binding chain that is simultaneously andcontinuously reacting on the surface of changing metal-oxide-carbide [50–52]. The composition of FTS products dif-fers essentially from the equilibrium composition [53–55].FTS is a process controlled by kinetics, and the distributionof products depends on the properties of catalysts and syn-thesis conditions. The main initial step is to adsorb H2 andCO on the metal surface. The activity and selectivity of cata-lysts depend mainly on the properties of CO adsorption-desorption-dissociation. Compared to H2, CO can beadsorbed on metal and oxide surfaces [56]. The simple rulesof FTS indicate that more olefins and carbon dioxide areformed on iron catalysts, whereas more alkanes and waterare produced on nickel and cobalt catalysts [53]. In hydro-thermal systems, carbon dioxide is the most likely reactant,
2 Geofluids
Daqing
Daqing
Zhaozhou
Anda
Potential area
Strike-slip fault
Commercial gas flow well
Logging with no oil or gas shown
Logging with oil or gas shown
Natural gas reservoir
Fault depression
100 km
10 km0
Xushen 27
Xushen 902
Xushen 9
Xushen 7
Xushen 302
Xushen 6
Xuzhong fault
Xushen 5
Xushen 1
Xushen 603
Xushen 141
Xushen 141
Xushen 12f1
f2
0
Xujiaweizi
Songli
ao Basi
n
Gas source fault
Failure area
(a)
Figure 1: Continued.
3Geofluids
Barremian
0-15
0040
0-13
0050
0-10
0080
2-20
00
Ser. StrataThickness
(m)Stage Form.
Hauterivian
Coal
Mudstone
Andesite
Rhyolite
Sand & conglomerate
Alb
ian
Apt
ian
Sour
c e ro
ckG
as re
serv
oir
Den
glou
kuYi
ngch
eng
Huo
shili
ngSh
ahez
i
Low
er C
reta
ceou
s
Silty mudstoneSand
Basalt
Silt
Tuff
(b)
Figure 1: Location of the Xujiaweizi Fault Depression (modified from [41]) and the stratigraphic column for the deep strata of Xujiaweizifault depression (modified from [36]).
4 Geofluids
and many laboratory experiments [57–63] have shown thatsaturated hydrocarbons and other organic compounds canbe generated by FTS reactions with carbon dioxide as an indi-rect carbon source. In addition, it has been suggested that inthis case, the first stage of the FTS reaction is to form CO byreducing CO2 by H2:
CO2 + H2 ⟷ CO +H2O 2
4. Experiments and Methods
4.1. Experimental Conditions and Materials. The Xujiaweizifault depression is a gas-bearing fault depression with thehighest exploration degree in the Songliao Basin. The burieddepth of the gas reservoir is generally 3000-4000m with anaverage of approximately 3500m [64]. The paleogeothermalgradient in the Xujiaweizi fault depression is higher thanthe present average value of 4°C/100m with a maximum of5°C/100m at the end of the Cretaceous (~65Ma) [65, 66].The maximum temperatures experienced by reservoirs andsource rocks thus occurred before the end of the Cretaceous,except in some areas where they may have been influenced byvolcanic activity [66, 67]. In this study, the chosen laboratoryconditions (380°C and 30MPa) of the Fischer-Tropsch syn-thesis experiments might be representative of the thermody-namic conditions of the Songliao reservoir. In addition, twotypes of material were selected to carry on the Fischer-Tropsch reaction, including the sodium materials, whichare NaHCO3 and NaBH4. NaHCO3 is prepared by CO2 thatis taken from the Fangshen-9 Well in the Songliao Basin,China. It has been established that the CO2 in theFangshen-9Well has an abiogenic origin. Therefore, the pur-pose of choosing CO2 in the Fangshen-9 Well to simulate theformation process of deep gas in the Songliao Basin was tomake the simulation as realistic as possible, allowing for theexploration of the origins of the gas. The CO2 and NaOHsolution is fully reacted and crystallized to obtain NaHCO3.After these two kinds of materials are mixed, the NaHCO3heating decomposition produces water that reacts withNaBH4 to produce the hydrogen. At a certain temperatureand pressure, the hydrogen and carbon dioxide undergoFischer-Tropsch synthesis. Magnetite is a ubiquitous compo-nent of ultramafic-hosted hydrothermal systems (Alt &Shanks, 2003), which is why it was selected for this series ofexperiments. Magnetite was used as the catalyst in the exper-iment, and the chemical reaction equation was as follows:
2NaHCO3 = Na2CO3 + H2O + CO2
NaBH4 + 2H2O = NaBO2 + 4H2
CO2 + H2 ⟶ CH4 + C2H6 + C3H8+⋯+H2O3
4.2. Experimental Procedure. The pyrolysis experiment wasconducted in a closed system following the proceduresdescribed in detail by Tao [68]. All pyrolysis experimentswere performed in gold cell reactors (50mm × 4mm).Approximately 5mg of NaBH4, 5mg of magnetite, and40mg of NaHCO3 prepared by CO2 were taken from theFangshen-9 Well in the Songliao Basin, China, and were
loaded into one gold tube, which was then welded on oneend. The gold tube was flushed with argon for approximately15 minutes to ensure complete removal of air and then sealedin an argon atmosphere using arc welding. After that, thesealed gold was placed in a stainless-steel pressure cooker,and then approximately 10ml of water was placed in a con-tainer connected to a pressurized water line. The pressuredevice consisted of an air compressor and a booster pumpthat drives high pressure water into an autoclave. The samplein the autoclave was heated to a target temperature in a singleoven. During pyrolysis, the pressure in the autoclave wasadjusted by adding water from the pump or removing waterfrom the autoclave through a leak valve. The experiment wascarried out at a temperature of 380°C and a pressure of30MPa for up to 72 h.
4.3. Product Analysis. The pyrolysis products of Fischer-Tropsch synthesis include hydrocarbon gases and nonhydro-carbon gases. In the analysis of hydrocarbon composition,the gold cell was placed in a vacuum system and pierced witha needle, and the gas products were released and collected bya Toppler pump for quantitative analysis. Then, the compo-sition of the gas products was analyzed using Agilent6890N-Wasson gas chromatography with a PoraPLOT Qcapillary column (50m × 0 53mm id). The oven temperaturewas maintained at 70°C for 6min, then increased from 70°Cto 130°C at 15°C/min, from 130°C to 180°C at 25°C/min,and then maintained at 180°C for 4min. Nitrogen was usedas a carrier gas, and experiments were carried out at 180°Cusing FID and TCD detectors. C1-C5 hydrocarbons, H2S,H2, and CO2 (detection limits of CO2 and H2: 40 ppmv;H2S: 150 ppmv; HC: 10ppmv; precision 2%; 10% at thedetection limit) were quantitatively analyzed by using theexternal standard method.
Gas carbon isotope analysis was performed by gaschromatography-isotope ratio mass spectrometry (GVIsoPrime™ GC-IRMS) with a capillary column(30m × 0 32mm). The temperature program was as follows:using helium as a carrier gas, the oven temperature was keptat 60°C for 3min, rose to 180°C with a 25°C/min heating pro-gram, then held at 180°C for 10min. Gas samples were ana-lyzed in duplicates, and the stable carbon isotopic valuesare reported in the δ-notation in per mil (‰) relative toVPDB. Precision for individual components in the molecularδ13C analysis is ±0.3‰.
GC-IRMS (Finnigan Delta Plus XL) with a capillary col-umn (HP-PLOT, 30m × 0 32mm) was used to analyze thehydrogen isotope of hydrocarbon gases (C1-C3). The temper-ature program is as follows: the temperature was held at 50°Cfor 7min, and then the temperature rose to 180°C at a rate of30°C/min. The stable hydrogen isotopic ratio (δ2H) valuesare reported in the δ-notation in per mil (‰) relative toVSMOW and the reproducibility and precision of isotopevalues are expected to be ±3‰.
5. Results and Discussion
5.1. Gas Isotope Composition. The Fischer-Tropsch synthesisexperiments were carried out under closed-system gold tube-
5Geofluids
high pressure vessels at 380°C and 30MPa. The gas yields andgas isotopic compositions are shown in Table 1. The resultsshow that the carbon isotopes (PDB, ‰) and hydrogenisotopes (SMOW, ‰) of gaseous hydrocarbons exhibitednormal order or partial reverse order, which is the reverseorder of methane and ethane, such as δ13C − C1 > δ13C −C2 < δ13C − C3 and δ2H − C1 > δ2H − C2 < δ2H − C3(Figure 2). Hu et al. [69] also observed that the carbon iso-topes have a reverse order or partial reverse order, whereasthe Fischer-Tropsch synthesis experiments were carried outunder a closed system with an iron-based catalyst for COand H2 at 270-300°C, 0.7-2.0MPa. Other scholars havereported that hydrogen isotopes show δ2H − C1 > δ2H −C2 < δ2H − C3 in a hydrothermal system; however, thecarbon isotopes of gaseous hydrocarbons are heavier withan increase in carbon number, and carbon isotopes have anormal order [21, 70]. Fu et al. [71] indicated that carbon iso-topes do not have a reverse order in a closed system with aniron-based catalyst for CO and H2 at 400
°C, 50MPa. In addi-tion, Fischer-Tropsch synthesis experiments were carried outin an open system with an iron-based catalyst for CO and H2at 260-300°C, 3MPa, by Taran et al. [72]; the results showedthat the carbon isotopes of gaseous hydrocarbons werereversed only for a low conversion rate of CO, and they con-sidered that other processes (such as a simple mixing of twoor more end members) or other P-T conditions of the carbonreduction could be responsible for the “inverse” isotopictrend found in meteorites and some natural gases. To thisend, FTS experiments were carried out while controllingthe NaBH4 content (Table 1). According to Zhang & Duan[73], the ethane was probably oxidized when the mantle-derived gas was migrated to the crust. Mantle fluids rose tothe boundary of lithosphere-asthenosphere, and the compo-sition of the fluids changed from the mixture of H2O-CH4-H2-C2H6 to the mixture of H2O-CO2-CO. The mantle fluidsH2/CO2 (mole ratio) are generally less than 1.2 under theconditions of high temperature and high pressure. The FTSexperimental gaseous hydrocarbons with the control ofNaBH4 carbon content and hydrogen isotope patterns areshown in Figure 3. When the H2/CO2 (mole ratio) is less than1.2, the gas carbon isotopes are a normal order and show alinear increase in carbon numbers; when the H2/CO2 (moleratio) is more than 1.2, the carbon isotopes of methane areheavier than ethane, and the carbon isotopes of C2+ areheavier and show a linear increase in carbon numbers. Whenthe H2/CO2 (mole ratio) is equal to or greater than 4.0, thecarbon isotopes have a reverse order. Compared to carbonisotopes, the hydrogen isotopes show δ2H − C1 < δ2H −C2 > δ2H − C3 when H2/CO2 (mole ratio) is less than 4.0,and the hydrogen isotopes of propane are close to ethanewith an increase in H2/CO2 (mole ratio). When H2/CO2(mole ratio) is equal to or greater than 4.0, the hydrogenisotopes of propane are heavier than ethane, and thehydrogen isotopes show a normal order.
5.2. The Characteristics of Abiogenic Gas. Sherwood Lollaret al. [74] used stable isotope signatures to suggest that CH4and higher hydrocarbon gases (ethane, propane, and butane)
at Kidd Creek mine on the Canadian Shield are pro-duced abiogenically by water-rock interactions, such assurface-catalyzed polymerization [24, 53], metamorphismof graphite-carbonate bearing rocks [75–77], and othergas-water-rock alteration reactions, such as serpentiniza-tion [20, 78–83].
According to Sherwood-Lollar et al. [11], the isotopicpattern of abiogenic gas of Precambrian Shield sites inCanada is shown in Figure 4(a). It was indicated that δ13Cof methane is the heaviest, which is distributed in -32‰~-36‰ (PDB); however, δ13C of ethane is in -36‰~-39‰which is the lightest in hydrocarbon gas, and C1-C2 shows adepletion trend while C2-C5 shows a consistent trend of iso-topic enrichment in 13C with increasing molecular weight.The pattern of hydrogen isotopic variation had consistent2H enrichment with increasing molecular weight, which is apositive sequence (Figure 4(b)). Proskurowski et al. (2008)pointed out that the carbon isotope compositions of C1 toC4 hydrocarbons from Lost City fluids are increasingly nega-tive (δ13C ranges from -9‰ to -16‰, PDB) with increasingchain length (Figure 4(a)). The hydrogen isotopic composi-tion of Lost City C1 to C3 hydrocarbons shows a similar,although less defined, trend in which molecules with longerchain lengths have similar or slightly lower δ2H values(-120‰ to -170‰, SMOW) relative to shorter-chain alkanes(Figure 4(b)). As shown in Figure 4, the carbon and hydrogenof the closed-system FTS gaseous hydrocarbon are distrib-uted between the Kidd Creek and Lost City.
5.3. The Deep Gas in the Songliao Basin and Abiogenic Gas
5.3.1. Gas Component. The composition of the deep SongliaoBasin hydrocarbon gas [41, 84], Fischer-Tropsch experimen-tal gas (Table 1), and the abiogenic gas of Kidd Creek [11] isshown in Figure 5. As shown in Figure 5, the deep SongliaoBasin hydrocarbon gas is similar to thermogenic gas but hasa different variation with abiogenic gas and has a trend of atransition to oceanic hydrothermal system abiogenic gas(Proskurowski et al. 2008). Therefore, the deep Basin gasmight be a mixture of the oil-type gas and the coal-formedgas, which could be the cause of the isotopic reverse; theclosed-system FTS gas is similar to the hydrothermal systemand has a trend of transition to the Kidd Creek (Figure 5).
5.3.2. Isotopic Characteristics. Previous studies have foundthat natural gases in the deep strata of the Songliao Basinare dominated by alkane gases, the carbon isotope com-position of methane is heavier (>-30.0‰) and the carbonisotopic reversal trend is general [41]. The carbon iso-topes of the deep Songliao Basin hydrocarbon gas becomemore depleted in 13C with increasing molecular mass(δ13C − C1 > δ13C − C2 > δ13C − C3 > δ13C − C4), which isa reverse order [41]. Wang et al. [84] suggested that naturalgases from the Songliao Basin show two different distribu-tion patterns of δ13C values due to differences in precursorsand mechanisms of hydrocarbon formation as well as thekinetic isotope fractionation of alkane carbon isotopes.Alkanes formed by the degradation of sedimentary organicmatter show lighter δ13C-C1 values (-30.2‰~-58.3‰) with
6 Geofluids
Table1:The
gasyields
andisotop
iccompo
sition
oftheFischer-Tropsch
synthesis.
Sample
T(°C)
P(M
Pa)
t(hr)
NaH
CO3(m
g)NaB
H4(m
g)Yields(m
l/gNaH
CO3)
δ13 C
(PDB,‰
)δ2H
(SMOW,‰
)C1
C2
C3
CO2
C4+C5
CO2
C1
C2
C3
C1
C2
C3
NaH
CO3+NaB
H4+Fe
3O4
380
306
37.07
3.89
1.38
0.18
0.09
0.05
0.04
-36.19
-19.09
-35.12
-33.81
-267.24
-456.62
-180.43
380
3018
32.88
5.78
14.10
0.53
0.18
0.08
0.10
-21.37
-20.37
-20.12
-17.63
-269.03
-326.79
-195.21
380
3036
36.22
5.52
15.86
0.59
0.22
0.07
0.12
-24.35
-25.93
-22.15
-18.17
-313.52
-305.48
-193.18
380
3054
34.33
4.88
18.04
0.69
0.24
0.04
0.16
-23.41
-18.99
-22.78
-18.31
-319.61
-322.91
-205.27
380
3072
36.92
5.04
15.86
0.86
0.20
0.03
0.09
-29.57
-13.47
-30.74
-24.73
-306.47
-276.12
-223.56
380
3072
39.98
0n.d.
n.d.
n.d.
26.23
n.d.
-4.94
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
380
3072
39.37
1.26
0.89
0.06
0.03
15.70
0.01
-22.14
-23.72
-33.76
-28.20
-420.10
ndnd
380
3072
40.56
3.84
9.10
0.45
0.17
1.75
0.09
-23.59
-17.00
-13.76
-13.77
-381.59
-296.53
-355.85
380
3072
39.61
5.17
12.03
0.76
0.26
0.04
0.17
-23.86
-24.48
-30.61
-25.30
-329.69
-280.31
-293.20
380
3072
41.75
6.86
19.01
0.81
0.23
0.05
0.05
-24.10
-17.14
-23.46
-21.42
-320.66
-222.56
-252.33
380
3072
40.79
8.48
33.01
4.58
2.26
0.04
1.18
-22.73
-23.79
-21.90
-23.72
-333.06
-240.58
-232.78
7Geofluids
a normal distribution of δ13C values for methane homo-logues. Abiogenic natural gases show heavier δ13C-C1 values(-30.5‰~-16.7‰) with a reverse distribution of δ13C valuessimilar to alkanes from the Murchison meteorite and poly-merization, whereas the δ2H values are featured by a normaldistribution. Figure 6 shows the carbon-hydrogen isotopevariation with carbon numbers (data from Proskurowskiet al. 2008; [11, 84]). As shown in Figure 6, the deepSongliao Basin gas isotopic pattern is different for both LostCity and Kidd Creek in which the deep Basin gas carbonisotopic pattern has a reverse order, and the pattern ofhydrogen has a normal order. The abiogenic gas of KiddCreek only shows δ13C − C1 > δ13C − C2, yet the carbonisotopes of C2+ have a normal order, and the carbon andhydrogen isotopes of the Lost City are the reverse order.
5.3.3. Isotope Fractionation. According to previouslyreported data ([21, 69, 71, 72]; Proskurowski et al. 2008;[84, 85]), the CO/CO2 and methane carbon isotope
fractionation diagram was added up for different naturalenvironments and experimental conditions (Figure 7). Over-all, the CO2 and methane carbon fractionation is between15‰ and 25‰ in the natural environments, and underexperimental conditions, the CO/CO2 and methane carbonisotope fractionation changed greatly between 8‰ and40‰, which is related to the conversion rate [69, 72]. Theconversion of CO/CO2 and carbon isotope fractionationhas a negative correlation. It should be noted that the meth-ane carbon isotope variation is limited to the deep SongliaoBasin gas which seems to have nothing to do with the CO2carbon isotope (Figure 7). The results suggest that the con-version of mantle CO2 to synthesize methane is low, andthere is a supplement of organic CO2, which implied thatthere is a complicated relationship between the two.
During the formation of abiogenic gas, hydrogen isotopefractionation also occurred (Figure 8). As shown in Figure 8,the carbon isotope and hydrogen isotope fractionation alloccurred in abiogenic synthesis to methane, and the
-10
-15
-20
-25
-30
-35
-401 2 3
Cn
�훿13
C (P
DB,
‰)
72 h54 h
36 h
6 h18 h
(a)
-100-150-200-250-300-350-400-450-500
1 2 3Cn
�훿D
(SM
OW
, ‰)
b
72 h54 h
36 h
6 h18 h
(b)
Figure 2: The isotopic pattern of the Fischer-Tropsch synthesis gas at different pyrolysis times. (a) The carbon isotopic pattern and (b) thehydrogen isotopic pattern.
-10
-15
-20
-25
-30
-35
-401 2 3
Cn
�훿13
C (P
DB,
‰) 2.91
4.003.400.572.312.49
1.90
H2/CO2
(a)
-100-150-200-250-300-350-400
1 2 3
-450-500
Cn
�훿D
(SM
OW
, ‰)
4.00
H2/CO2
3.682.311.670.66
0.57
(b)
Figure 3: The isotopic pattern of closed-system FTS with the control of NaBH4 content. (a) The carbon isotopic pattern and (b) the hydrogenisotopic pattern.
8 Geofluids
-40
-36
-32
-28
-24
-20
-16
-12
-8
1 2 3Cn
This study
Kidd creek
Lost city
�훿13
C (P
DB,
‰)
(a)
-100-150-200-250-300-350-400
1 2 3
-450-500
Cn
Lost city
This study
Kidd creek
�훿D
(SM
OW
, ‰)
(b)
Figure 4: The isotopic pattern of abiogenic gas. (a) The carbon isotopic pattern and (b) the hydrogen isotopic pattern; for comparison, theδ13C and δ2H values for abiogenic gases occurring at Lost City (Proskurowski et al. 2008) and Kidd Creek [74] are also shown.
1000
100
10
11 10 100 1000
�is studyKidd creekLost city
C1/C2
C 2/C 3
�e deep Songliao Basin gasOil-type gas
Coal-formed gas
Figure 5: Chemical components of the deep Songliao Basin gas andabiogenic gas (the deep Songliao Basin hydrocarbon gas: [84]; theoil-type gas and the coal-formed gas: [68]; Kidd Creek: [11]; Lostcity: Proskurowski et al. 2008).
-10-20-30-40
-50
-100
-150
-200
-250
-300
-350
-400
-450
-500
1
2
3
4
Kidd creek
12
3
Lost city
2
1
33
2
Sheng2-1
Fangsheng2
Fangsheng1-2
�훿13 C (PDB, ‰)
�훿D
(SM
OW
, ‰)
1
2 This study
122
3
Figure 6: Natural gas carbon-hydrogen isotope variation withcarbon number (the deep Songliao Basin hydrocarbon gas: [84];Kidd Creek: [11]; Lost city: Proskurowski et al. 2008).
9Geofluids
carbon isotope fractionation increased with the conversionas the hydrogen isotope fractionation decreased with theconversion. It is estimated that the methane carbon iso-tope fractionation was in the 20‰ and 25‰, and the earlyhydrogen isotope fractionation was 170‰ while the latefractionation was 80‰. The carbon isotope and hydrogenisotope fractionation of the condensate oil was 20‰ and180‰. Closed-system Fischer-Tropsch synthesis experi-mental data (Table 1) shows that a carbon isotope ofmethane has increased with a decrease in C1/C2, whichmeans that the carbon isotope fractionation is reducedand is probably related to high conversion and polymeri-zation [11, 84].
6. Conclusion
Closed-system Fischer-Tropsch synthesis and pyrolysis werecarried out at 380°C and 30MPa; the experimental data andthe isotopic composition of abiogenic gas were systematicallystudied, and the deep Songliao Basin gas was also investi-gated in this study, producing following preliminaryconclusions:
(1) The results show that carbon isotopes and hydrogenisotopes of Fischer-Tropsch synthesis gaseous hydrocarbonsexhibit normal order or partial reverse order, which is thereverse order of methane and ethane such that δ13C − C1 >δ13C − C2 < δ13C − C3 and δ2H − C1 > δ2H − C2 < δ2H − C3.
0
-10
-20
-30
-40
-50
CO2
CH4
Dissoved CO2
CO2
CO
36‰
31‰
8-26
‰
21-4
2‰
Hot springsof China
�e deep SogliaoBasin gas
Oceanic hydrothermalsystem
Hydrothermal systemFischer-tropsch
Open-systemFischer-tropsch
Closed-systemFischer-tropsch
Siderite
�훿13
C (P
DB,
‰)
Figure 7: Carbon isotope fractionation under different conditions (data from [21, 69, 71, 72]; Proskurowski et al. 2008; [84, 85]).
Figure 8: Carbon-hydrogen isotope fractionation under different experimental conditions (data from [21, 72]).
10 Geofluids
(2) It is suggested that carbon isotopes of gaseous hydro-carbons showed a reversal or a reverse order only at low con-version rates of CO2; when the H2/CO2 (mole ratio) is equalto or greater than 4.0, the carbon isotopes show a reverseorder, while the hydrogen isotopes show a normal order.
(3) The gas component and isotopic pattern suggeststhat the deep Songliao Basin gas might be a mixture ofoil-type gas and coal-formed gas, which could be the causeof the isotopic reverse.
Data Availability
The experimental data used to support the findings of thisstudy are included within the article.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
Acknowledgments
This work was financially supported by the Chinese Acad-emy of Sciences Key Project (Grant Nos. XDB10010202and XDB10030404), the National Natural Science Foun-dation of China (Grant Nos. 41572350 and 41503049),the National Key R&D Program of China (Grant No.2017YFA0604803), the Western Light Project and the KeyLaboratory Project of Gansu (Grant No. 1309RTSA041).
References
[1] D. D. Rice and G. E. Claypool, “Generation accumulation andresource potential of biogenic gas,” AAPG Bulletin, vol. 65,pp. 5–25, 1981.
[2] M. Schoell, “Multiple origins of methane in the earth,” Chem-ical Geology, vol. 71, pp. 1–10, 1988.
[3] M. J. Whiticar, E. Faber, and M. Schoell, “Biogenic methaneformation in marine and freshwater environments: CO2reduction vs. acetate fermentation-isotope evidence,” Geochi-mica et Cosmochimica Acta, vol. 50, no. 5, pp. 693–709, 1986.
[4] M. Schoell, “The hydrogen and carbon isotopic composition ofmethane from natural gases of various origins,” Geochimica etCosmochimica Acta, vol. 44, pp. 649–661, 1980.
[5] B. Capaccioni, Y. Taran, F. Tassi, O. Vaselli, G. Mangani, andJ. L. Macias, “Source conditions and degradation processes oflight hydrocarbons in volcanic gases: an example from El Chi-chón volcano (Chiapas State, Mexico),” Chemical Geology,vol. 206, no. 1-2, pp. 81–96, 2004.
[6] J. Fiebig, A. B. Woodland, J. Spangenberg, and W. Oschmann,“Natural evidence for rapid abiogenic hydrothermal genera-tion of CH4,” Geochimica et Cosmochimica Acta, vol. 71,no. 12, pp. 3028–3039, 2007.
[7] Y. Wang, S. Zhang, and G. Yuce, “Gas geochemistry: fromconventional to unconventional domains,” Marine and Petro-leum Geology, vol. 89, pp. 1–3, 2018.
[8] G. Etiope, M. Schoell, and H. Hosgormez, “Abiotic methaneflux from the Chi-maera seep and Tekirova ophiolites(Turkey): understanding gas exhalation from low temperatureserpentinization and implications for Mars,” Earth and Plane-tary Science Letters, vol. 310, no. 1-2, pp. 96–104, 2011.
[9] G. Etiope and B. Sherwood Lollar, “Abiotic methane onearth,” Reviews of Geophysics, vol. 51, no. 2, pp. 276–299,2013.
[10] M. A. Sephton and R. M. Hazen, “On the origins of deephydrocarbons,” Reviews in Mineralogy and Geochemistry,vol. 75, no. 1, pp. 449–465, 2013.
[11] B. S. Lollar, G. Lacrampe-Couloume, K. Voglesonger, T. C.Onstott, L. M. Pratt, and G. F. Slater, “Isotopic signatures ofCH4 and higher hydrocarbon gases from Precambrian Shieldsites: a model for abiogenic polymerization of hydrocarbons,”Geochimica et Cosmochimica Acta, vol. 72, no. 19, pp. 4778–4795, 2008.
[12] G. Yuce, F. Italiano, W. D'Alessandro et al., “Origin andinteractions of fluids circulating over the Amik Basin (Hatay,Turkey) and relationships with the hydrologic, geologic andtectonic settings,” Chemical Geology, vol. 388, pp. 23–39,2014.
[13] T. Boschetti, G. Etiope, and L. Toscani, “Abiotic methane inthe hyperalkaline springs of Genova. Italy,” Procedia Earthand Planetary Science, vol. 7, pp. 248–251, 2013.
[14] C. Boulart, V. Chavagnac, C. Monnin, A. Delacourt,G. Ceuleneer, and G. Hoareau, “Difference in gas venting fromultramafic-hosted warm springs: the example of Oman andVoltri ophiolites,” Ofioliti, vol. 38, pp. 143–156, 2013.
[15] W. D'Alessandro, G. Yüce, F. Italiano et al., “Large composi-tional differences in the gases released from the Kizildagophiolitic body (Turkey): evidences of prevailingly abiogenicorigin,” Marine and Petroleum Geology, vol. 89, pp. 174–184,2018.
[16] G. Etiope, “Abiotic methane in continental serpentinizationsites: an overview,” Procedia Earth and Planetary Science,vol. 17, pp. 9–12, 2017.
[17] Y. Sano, A. Urabe, H. Wakita, and H. Wushiki, “Origin ofhydrogen-nitrogen gas seeps, Oman,” Applied Geochemistry,vol. 8, no. 1, pp. 1–8, 1993.
[18] C. Vacquand, E. Deville, V. Beaumont et al., “Reduced gasseepages in ophiolitic complexes: evidences for multiple ori-gins of the H2-CH4-N2 gas mixtures,” Geochimica et Cosmo-chimica Acta, vol. 223, pp. 437–461, 2018.
[19] G. Etiope, N. Samardžić, F. Grassa, H. Hrvatović, N. Miošić,and F. Skopljak, “Methane and hydrogen in hyperalkalinegroundwaters of the serpentinized Dinaride ophiolite belt,Bosnia and Herzegovina,” Applied Geochemistry, vol. 84,pp. 286–296, 2017.
[20] J. Horita andM. E. Berndt, “Abiogenic methane formation andisotopic fractionation under hydrothermal conditions,” Sci-ence, vol. 285, no. 5430, pp. 1055–1057, 1999.
[21] T. M. McCollom and J. S. Seewald, “Carbon isotope composi-tion of organic compounds produced by abiotic synthesisunder hydrothermal conditions,” Earth and Planetary ScienceLetters, vol. 243, no. 1-2, pp. 74–84, 2006.
[22] B. Sherwood Lollar, S. K. Frape, S. M. Weise, P. Fritz, S. A.Macko, and J. A. Welhan, “Abiogenic methanogenesis in crys-talline rocks,” Geochimica et Cosmochimica Acta, vol. 57,no. 23-24, pp. 5087–5097, 1993.
[23] F. Fischer and H. Tropsch, “Hydrocarbon synthesis atatmospheric pressures from gasification products of coal,”Branntoff Chemistry, vol. 7, pp. 97–104, 1926.
[24] D. I. Foustoukos and SeyfriedWE Jr, “Hydrocarbons in hydro-thermal vent fluids: the role of chromium-bearing catalysts,”Science, vol. 304, no. 5673, pp. 1002–1005, 2004.
11Geofluids
[25] J. Horita, “Some perspectives on isotope biosignatures for earlylife,” Chemical Geology, vol. 218, no. 1-2, pp. 171–186, 2005.
[26] M. S. Lancet and E. Anders, “Carbon isotope fractionation inthe Fischer-Tropsch synthesis and in meteorites,” Science,vol. 170, no. 3961, pp. 980–982, 1970.
[27] S. Salvi and A. E. Williams-Jones, “Fischer-Tropsch synthesisof hydrocarbons during sub-solidus alteration of the StrangeLake peralkaline granite, Quebec/Labrador, Canada,” Geo-chimica et Cosmochimica Acta, vol. 61, no. 1, pp. 83–99,1997.
[28] E. L. Shock, “Geochemical constraints on the origin of organiccompounds in hydrothermal systems,”Origins of Life and Evo-lution of the Biosphere, vol. 20, no. 3-4, pp. 331–367, 1990.
[29] G. Yuen, N. Blair, D. J. Des Marais, and S. Chang, “Carbon iso-tope composition of low molecular weight hydrocarbons andmonocarboxylic acids from Murchison meteorite,” Nature,vol. 307, no. 5948, pp. 252–254, 1984.
[30] T. J. Gold, “Terrestrial sources of carbon and earthquake out-gassing,” Journal of Petroleum Geology, vol. 1, no. 3, pp. 3–19,1979.
[31] N. G. Holm and J. L. Charlou, “Initial indications of abioticformation of hydrocarbons in the rainbow ultramafic hydro-thermal system, Mid-Atlantic Ridge,” Earth and PlanetaryScience Letters, vol. 191, no. 1-2, pp. 1–8, 2001.
[32] D. S. Kelley, J. A. Karson, G. L. Früh-Green et al., “Aserpentinite-hosted ecosystem: the Lost City hydrothermalfield,” Science, vol. 307, no. 5714, pp. 1428–1434, 2005.
[33] J. Potter, A. H. Rankin, and P. J. Treloar, “Abiogenic Fischer-Tropsch synthesis of hydrocarbons in alkaline igneous rocks;fluid inclusion, textural and isotopic evidence from theLovozero complex, N.W. Russia,” Lithos, vol. 75, no. 3-4,pp. 311–330, 2004.
[34] J. X. Dai, Y. Song, C. S. Dai, A. F. Chen, M. L. Sun, Y. S. Liaoet al., Conditions Governing the Formation of Abiogenic Gasand Gas Pools in the Eastern China, Science Press, Beijing,China, 2000.
[35] J. X. Dai, “Potential areas for coal-formed gas exploration inChina,” Petroleum Exploration and Development, vol. 34,no. 6, pp. 641–645, 2007.
[36] H. S. Zeng, J. K. Li, and Q. L. Huo, “A review of alkane gas geo-chemistry in the Xujiaweizi fault-depression, Songliao Basin,”Marine and Petroleum Geology, vol. 43, pp. 284–296, 2013.
[37] J. Dai, Y. Ni, J. Li et al., Geochemical Characteristics of theAbiogenic Alkane Gases in the Songliao Basin, China, AAPGHedberg Conference Natural Gas Geochemistry, Beijing,China, 2011.
[38] H. Huang, J. Yang, Y. Yang, and X. du, “Geochemistry of nat-ural gases in deep strata of the Songliao Basin, NE China,”International Journal of Coal Geology, vol. 58, no. 4, pp. 231–244, 2004.
[39] J. Li, W. Fang, H. Zeng, W. Liu, Y. Zou, and J. Liu, “Possibleorigins for inverse stable carbon isotopes of gaseous alkanesfrom the Xujiaweizi fault depression,” Acta Petrolei Sinica,vol. 32, pp. 54–61, 2011.
[40] J. Mi, S. Zhang, G. Hu, and K. He, “Geochemistry of coal-measure source rocks and natural gases in deep formationsin Songliao Basin, NE China,” International Journal of CoalGeology, vol. 84, no. 3-4, pp. 276–285, 2010.
[41] N. Yunyan, D. Jinxing, Z. Qinghua, L. Xia, H. Anping, andY. Chun, “Geochemical characteristics of abiogenic gas andits percentage in Xujiaweizi Fault Depression, Songliao Basin,
NE China,” Petroleum Exploration and Development, vol. 36,no. 1, pp. 35–45, 2009.
[42] J. X. Dai, “Identification of various genetic natural gases,”China Offshore Oil and Gas, vol. 6, no. 1, pp. 11–19, 1992.
[43] Z. Q. Guo and X. B. Wang, “Discussions on abiogenic gases inthe Songliao Basin,” Science in China (Series B), vol. 24, no. 3,pp. 303–309, 1994.
[44] Y. F. Yang, Q. Zhang, H. P. Huang et al., “Abiogenic naturalgases and their accumulation model in Xujiaweizi area,Songliao Basin, Northeast China,” Earth Science Frontiers,vol. 7, no. 4, pp. 523–533, 2000.
[45] H. P. Huang, “Isotopic reversal in natural gas: an example ofdeep-strata gases from Xujiaweizi depression, Songliao Basin,”Earth Science-Journal of China University of Geosciences,vol. 25, no. 6, pp. 617–623, 2000.
[46] C.W. Huang, “The 10 great advances of petroleum science andtechnology of CNPC in 2010,” Petroleum Exploration andDevelopment, vol. 38, no. 2, p. 144, 2011.
[47] Y. Shang and S. M. Shi, “Geochemical characteristics and gen-eses of the deep natural gas in Xijiaweizi fault depression,”Petroleum Geology and Oilfield Development in Daqing,vol. 34, no. 2, pp. 19–25, 2015.
[48] Z. Q. Feng, “Volcanic rocks as prolific gas reservoir: a casestudy from the Qingshen gas field in the Songliao Basin, NEChina,” Marine and Petroleum Geology, vol. 25, no. 4-5,pp. 416–432, 2008.
[49] G. P. Glasby, “Abiogenic origin of hydrocarbons: an historicaloverview,” Resource Geology, vol. 56, no. 1, pp. 83–96, 2006.
[50] A. Raje and B. H. Davis, “Fischer-Tropsch synthesis: mecha-nism studies using isotopes,” in Catalysis, Volume 12, J. J.Spring, Ed., pp. 52–131, The Royal Society of Chemistry, 1996.
[51] A. Steynberg and M. Dry, Fischer-Tropsch Technology,Elsevier, 2004.
[52] G. P. Van der Laan, A. A. Beenacker, and C. M. Beenacker,“Kinetics and selectivity of the Fischer-Tropsch synthesis: a lit-erature review,” Catalysis Reviews: Science and Engineering,vol. 41, no. 3-4, pp. 255–318, 1999.
[53] R. B. Anderson, The Fischer-Tropsch Synthesis, AcademicPress, Orlando, 1984.
[54] L. S. Glebov and G. A. Kliger, “Molecular-weight distributionof the Fischer-Tropsch synthesis products,” Russian ChemicalReviews, vol. 63, pp. 192–202, 1994.
[55] B. Shi and B. H. Davis, “Fischer-Tropsch synthesis: accountingfor chain-length related phenomena,” Applied Catalysis A:General, vol. 277, no. 1-2, pp. 61–69, 2004.
[56] A. L. Lapidus and A. Y. Krylova, “On the mechanism of form-ing of liquid hydrocarbons on co-catalyst,” Russian chemicaljournal, vol. 1, pp. 44–55, 2000.
[57] T. M. McCollom and B. R. T. Simoneit, “Abiotic formation ofhydrocarbons and oxygenated compounds during thermaldecomposition of iron oxalate,” Origins of Life and Evolutionof the Biosphere, vol. 29, no. 2, pp. 167–186, 1999.
[58] T. M. McCollom, “Experimental investigation of abiotic syn-thesis of organic compounds under hydrothermal conditions,”Book of Abstracts 2000; 219th ACS National Meeting, 2000, SanFrancisco, CA, USA, March 26-30, 2000, 2000GEOC-028.
[59] A. I. Rushdi and B. R. T. Simoneit, “Abiotic condensation syn-thesis of glyceride lipids and wax esters under simulatedhydrothermal conditions,”Origins of Life and Evolution of Bio-spheres, vol. 36, no. 2, pp. 93–108, 2006.
12 Geofluids
[60] A. I. Rushdi and B. R. T. Simoneit, “Abiotic synthesis oforganic compounds from carbon disulfide under hydrother-mal conditions,” Astrobiology, vol. 5, no. 6, pp. 749–769, 2005.
[61] A. I. Rushdi and B. R. T. Simoneit, “Condensation reactionsand formation of amides, esters, and nitriles under hydrother-mal conditions,” Astrobiology, vol. 4, no. 2, pp. 211–224, 2004.
[62] A. I. Rushdi and B. R. T. Simoneit, “Lipid formation by aque-ous Fischer-Tropsch-type synthesis over a temperature rangeof 100 to 400 degrees C,” Origins of Life and Evolution of theBiosphere, vol. 31, no. 1/2, pp. 103–118, 2001.
[63] J. S. Seewald, M. Y. Zolotov, and T. McCollom, “Experimentalinvestigation of single carbon compounds under hydrothermalconditions,” Geochimica et Cosmochimica Acta, vol. 70, no. 2,pp. 446–460, 2006.
[64] M. Wang, Y. F. Sun, W. G. Wang, Y. Wang, and L. Shi, “Gasgeneration characteristics and resource potential of the deepsource rock in Xujiaweizi fault depression, northern SongliaoBasin,” Natural Gas Geoscience, vol. 25, no. 7, pp. 1011–1018, 2014.
[65] J. Li, W. Liu, and L. Song, “A study of hydrocarbon generationconditions of deep source rocks in Xujiaweizi fault depressionof the Songliao Basin,” Natural Gas Industry, vol. 26, pp. 21–24, 2006.
[66] Q. Zhou, Z. Feng, and G. Men, “Present geotemperature andits suggestion to natural gas generation in Xujiaweizi fault-depression of the northern Songliao Basin,” Science in ChinaSeries D: Earth Sciences, vol. 51, no. S1, pp. 207–220, 2008.
[67] J. Xiao, H. Chen, S. Yang et al., “Gas charging of deep volcanicreservoirs in the northern Songliao Basin: evidence from fluidinclusions,” Acta Petrolei Sinica, vol. 32, pp. 968–975, 2011.
[68] W. Tao, Experiments on Natural Gas Generation, Oil Crackingand FTS under High Pressure: Experiments, Kinetics and a CaseStudy, Guangzhou Institute of Geochemistry, ChineseAcademy of Sciences, Guangzhou, China, 2008.
[69] G. X. Hu, Z. Y. OuYang, X. B. Wang, and Q. B. Wen, “TheFischer-Tropsch reaction of carbon isotope fractionationunder the conditions of the original solar nebula,” Science inChina (Series D), vol. 27, no. 5, pp. 395–400, 1997.
[70] F. W. Ji, H. Y. Zhou, and Q. H. Yang, “Abiogenic synthesis ofbutane and pentane from CO2 and H2 under hydrothermalconditions,” Geochemica, vol. 36, no. 2, pp. 171–175, 2007.
[71] Q. Fu, B. Sherwood Lollar, J. Horita, G. Lacrampe-Couloume,and W. E. Seyfried Jr, “Abiotic formation of hydrocarbonsunder hydrothermal conditions: constraints from chemicaland isotope data,” Geochimica et Cosmochimica Acta, vol. 71,no. 8, pp. 1982–1998, 2007.
[72] Y. A. Taran, G. A. Kliger, and V. S. Sevastianov, “Carbon iso-tope effects in the open-system Fischer-Tropsch synthesis,”Geochimica et Cosmochimica Acta, vol. 71, no. 18, pp. 4474–4487, 2007.
[73] C. Zhang and Z. H. Duan, “A model for C-O-H fluid in theEarth’s mantle,” Geochimica et Cosmochimica Acta, vol. 73,no. 7, pp. 2089–2102, 2009.
[74] B. Sherwood Lollar, T. D. Westgate, J. A. Ward, G. F. Slater,and G. Lacrampe-Couloume, “Abiogenic formation of alkanesin the Earth’s crust as a minor source for global hydrocarbonreservoirs,” Nature, vol. 416, no. 6880, pp. 522–524, 2002.
[75] A. A. Giardini and C. A. Salotti, “Kinetics and relations in thecalcite-hydrogen reaction and relations in the dolomite-hydrogen and siderite-hydrogen systems,” American Mineral-ogist, vol. 54, pp. 1151–1172, 1969.
[76] J. R. Holloway, “Graphite-CH4-H2O-CO2 equilibria at low-grade metamorphic conditions,” Geology, vol. 12, no. 8,pp. 455–458, 1984.
[77] J. F. Kenney, V. A. Kutcherov, N. A. Bendeliani, and V. A.Alekseev, “The evolution of multicomponent systems at highpressures: VI. The thermodynamic stability of the hydrogen-carbon system: The genesis of hydrocarbons and the originof petroleum,” Proceedings of the National Academy ofSciences, vol. 99, no. 17, pp. 10976–10981, 2002.
[78] M. E. Berndt, D. E. Allen, and W. E. J. Seyfried, “Reduction ofCO2 during serpentinization of olivine at 300 °C and 500 bar,”Geology, vol. 24, no. 4, pp. 351–354, 1996.
[79] J. L. Charlou, J. P. Donval, Y. Fouquet, P. Jean-Baptiste, andN. Holm, “Geochemistry of high H2 and CH4 vent fluids issu-ing from ultramafic rocks at the rainbow hydrothermal field(36°14′N, MAR),” Chemical Geology, vol. 191, no. 4,pp. 345–359, 2002.
[80] J. L. Charlou and J. P. Donval, “Hydrothermal methane vent-ing between 12°N and 26°N along the Mid-Atlantic Ridge,”Journal of Geophysical Research, vol. 98, no. B6, pp. 9625–9642, 1993.
[81] D. S. Kelley, J. A. Karson, D. K. Blackman et al., “An off-axishydrothermal vent field near the Mid-Atlantic Ridge at30°N,” Nature, vol. 412, no. 6843, pp. 145–149, 2001.
[82] T. M. McCollom and J. S. Seewald, “A reassessment of thepotential for reduction of dissolved CO2 to hydrocarbons dur-ing serpentinization of olivine,” Geochimica et CosmochimicaActa, vol. 65, no. 21, pp. 3769–3778, 2001.
[83] D. A. Vanko and D. S. Stakes, “Fluids in oceanic layer 3: evi-dence from veined rocks, hole 735B, Southwest Indian Ridge,”Proceedings of the Ocean Drilling Program, Scientific Results,vol. 118, pp. 181–215, 1991.
[84] X. Wang, Z. Guo, J. Tuo et al., “Abiogenic hydrocarbons incommercial gases from the Songliao Basin,” Science in China(Series D), vol. 52, no. 2, pp. 213–226, 2009.
[85] J. X. Dai, C. N. Zou, S. C. Zhang et al., “Identification the originof inorganic and organic alkane,” China. Sci. China, Ser. D,vol. 38, no. 11, pp. 1329–1341, 2008.
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