Molecular and carbon isotopic variation in 3.5 years shale gas production from Longmaxi Formation in Sichuan Basin, China

Zhang, Mingjie; Tang, Qingyan; Cao, Chunwei; Lv, Zonggang; Zhang, Tongwei; Zhang, Dekuan; Li, Zhongping; Du, Lidong

doi:10.1016/j.marpetgeo.2017.01.023

Cited by 49 publications

(19 citation statements)

References 42 publications

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“…The volatiles of different origins exhibit markedly different C, He, Ne, and Ar isotopic compositions, which can be used to reveal their sources [10,21,22,28,37,48]. The 3 He/ 4 He and 40 Ar/ 36 Ar ratios in the Podong intrusion are mainly plotted around the atmosphere (ATM) with a trend toward continental crust and old oceanic crust endmembers [22,29,39,49] (crust, Figure 6).…”

Section: Discussionmentioning

confidence: 99%

“…The correlations between 3 He/ 4 He ratio vs. both 40 Ar/ 36 Ar and δ 13 C CO 2 indicated the contribution from altered oceanic crust (AOC, Figures 6 and 8) in the Podong intrusion [64,65]. δ 13 C 2 > δ 13 C 3 in most samples demonstrate type I organic materials from oceanic sedimentary [48]. The δ 13 C CO 2 and δ 13 C CH 4 variations in the Podong volatiles are suggestive of methane oxidative activity (Figure 8(a)), which provides further evidence of a contribution from altered oceanic crust [10].…”

Section: The Petrogenesis and Dynamic Settings Of Intrusionmentioning

confidence: 90%

“…It is also supported by sulfur isotopes of sulfide separates (0.82-2.02‰) [3], similar to typical mantle values (0 ± 2‰). The thermogenic origin refers to the gases formed by thermal decomposition of biogenic organic matter under high geological temperature and pressure conditions and implies a sedimentary source [48]. The crust and thermogenic origins are supported by a normal carbon isotopic distribution pattern (Figure 4(a)).…”

Section: Geofluidsmentioning

confidence: 94%

“…The CO 2 and hydrocarbon gases from different origins show distinct carbon isotopic compositions and distribution patterns, which can be used to constrain various terrestrial reservoirs [10,21,22,37,48,51]. The CO 2 and CH 4 released at 200-400°C were mainly released from secondary fluid inclusions and cracked primary fluid inclusions (Figure 3(b)), since the atmospheric component adsorbed in the samples is generally degassed at low temperature during step heating [49].…”

Section: Geofluidsmentioning

confidence: 99%

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The Petrogenesis of the Permian Podong Ultramafic Intrusion in the Tarim Craton, Western China: Constraints from C-He-Ne-Ar Isotopes

Zhang

Feng

et al. 2019

Geofluids

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The Podong Permian ultramafic intrusion is only one ultramafic intrusion with massif Ni-Cu sulfide mineralization in the Pobei layered mafic-ultramafic complex, western China. It is obviously different in sulfide mineralization from the nearby coeval Poyi ultramafic intrusion with the largest disseminated Ni-Cu sulfide mineralization and mantle plume contribution (Zhang et al., 2017). The type and addition mechanism of the confirmed crustal contaminations and possible mantle plume involved in the intrusion formation require evidences from carbon and noble gas isotopic compositions. In the present study, we have measured C, He, Ne, and Ar isotopic compositions of volatiles from magmatic minerals in the Podong ultramafic intrusion. The results show that olivine, pyroxene, and plagioclase minerals in the Podong intrusion have variable δ13C of CO2 (-24.5‰ to -3.2‰). The CH4, C2H6, C3H8, and C4H10 hydrocarbon gases show normal or partial reversal distribution patterns of carbon isotope with carbon number and light δ13C1 value of CH4, indicating the hydrocarbon gases of biogenic origin. The δ13C of CO2 and CH4 suggested the magmatic volatile of the mantle mixed with the volatiles of thermogenic and crustal origins. Carbon and noble gas isotopes indicated that the Podong intrusion could have a different petrogenesis from the Poyi ultramafic intrusion. Two types of contaminated crustal materials can be identified as crustal fluids from subducted altered oceanic crust (AOC) in the lithospheric mantle source and a part of the siliceous crust. The carbon isotopes for different minerals show that magma spent some time crystallizing in a magma chamber during which assimilation of crustal material occurred. Subduction-devolatilization of altered oceanic crust could be the best mechanism that transported large proportion of ASF (air-saturated fluid) and crustal components into the mantle source. The mantle plume existing beneath the Poyi intrusion could provide less contribution of real materials of silicate and fluid components.

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Section: Discussionmentioning

confidence: 99%

Section: The Petrogenesis and Dynamic Settings Of Intrusionmentioning

confidence: 90%

Section: Geofluidsmentioning

confidence: 94%

Section: Geofluidsmentioning

confidence: 99%

See 2 more Smart Citations

The Petrogenesis of the Permian Podong Ultramafic Intrusion in the Tarim Craton, Western China: Constraints from C-He-Ne-Ar Isotopes

Zhang

Feng

et al. 2019

Geofluids

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“…Previous studies have shown that there is intrusion of lower oil-type gas into the natural gas in the northern part of the basin (Yin Feng et al, 2013;Guo Tonglou, 2013;Li Yanjun, 2013;Xie Xiaoqin et al, 2014;Wang Wanchun et al, 2014;Hu Wei et al, 2014;Wu Xiaoqi et al, 2015). The carbon isotope inversion of alkane gas resulting from "identical source rocks from different periods" or "identical types from different source rocks" is common in both domestic China and abroad Jenden et al, 1993;Xie Zengye et al, 1999;Burruss et al, 2010;Barbala et al, 2011;Zumberge et al, 2012;Tilley et al, 2013;Xia et al, 2013;Wei Guoqi et al, 2014;Zhu Guangyou et al, 2014;Yang et al, 2017;Zhang et al, 2017). In addition to δ 13 C 1 >δ 13 C 2 , many occasions of δ 13 C 3 >δ 13 C 4 and a few occasions of δ 13 C 2 >δ 13 C 3 occurred in the natural gas from the Xujiahe Formation.…”

Section: Oct 2017mentioning

confidence: 99%

Geochemical Characteristics of the Upper Triassic Xujiahe Formation in Sichuan Basin, China and its Significance for Hydrocarbon Accumulation

Xie

et al. 2017

Acta Geologica Sinica (Eng)

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The alternative development of coal‐bearing hydrocarbon source rocks and low‐porosity and low‐permeability tight sandstone reservoirs of the Triassic Xujiahe Formation in the Sichuan Basin is favorable for near‐source hydrocarbon accumulation. The natural gas composition of the Xujiahe Formation in the Sichuan Basin is dominated by hydrocarbon gases, of which the methane content is 80.16%–98.67%. Typically, the C2+ content is larger than 5% in main wet gas. The dry gas is mainly distributed in the western and northern regions of the basin. The non‐hydrocarbon gases mainly contain nitrogen, carbon dioxide, hydrogen, and helium, with a total content of <2%. The carbon isotope ranges of methane and its homologues in natural gas are: δ13C1 of −43.8‰ to −29.6‰, δ13C2 of −35.4‰ to −21.5‰, δ13C3 of −27.6‰ to −19.8‰, and δ13C4 of −27.7‰ to −18.8‰. δ13C3>δ13C4 occurs in some natural gas with a low evolution degree; such gas is mainly coal‐related gas from humic‐type source rocks of the Xujiahe Formation. As for the natural gas, δ2HCH4 values ranged from −195‰ to −161‰, δ2HC2H6 values ranged from −154‰ to −120‰, and δ2HC3H8 values ranged from −151‰ to −108‰. The dry coefficient, δ13C and δ2HCH4 are all positively correlated with the maturity of source rocks. The higher the maturity of source rocks is, the larger the natural gas dry coefficient is and the larger the δ13C and δ2HCH4 values are, indicative of the characteristic of near‐source accumulation. The δ2HC2H6 value of natural gas is influenced by paleosalinity to a relatively large extent; the higher the paleosalinity is, the larger the δ2HC2H6 value is. The Pr/Ph value of the condensate oil ranged from 1.60 to 3.43, illustrating light oxidization–light reduction and partial‐oxidization characteristics of the depositional environment of coal‐bearing source rocks of the Xujiahe Formation. The natural gas light hydrocarbon (C5–C7) from the Xujiahe Formation presented two characteristics: the first was the relatively high aromatic hydrocarbon content (19%–32.1%), which reveals the characteristic of natural gas with humic substances of high‐maturity; the second was the low content of aromatic hydrocarbon (0.4%–9.3%), reflecting water‐washing during the accumulation of the natural gas. The reported research outcomes indicate a potential mechanism for natural gas accumulation in the Xujiahe Formation, which will further guide natural gas exploration in this region.

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Carbon isotope fractionation during shale gas transport: Mechanism, characterization and significance

et al. 2020

Sci. China Earth Sci.

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Molecular and carbon isotopic variation in 3.5 years shale gas production from Longmaxi Formation in Sichuan Basin, China

Cited by 49 publications

References 42 publications

The Petrogenesis of the Permian Podong Ultramafic Intrusion in the Tarim Craton, Western China: Constraints from C-He-Ne-Ar Isotopes

The Petrogenesis of the Permian Podong Ultramafic Intrusion in the Tarim Craton, Western China: Constraints from C-He-Ne-Ar Isotopes

Geochemical Characteristics of the Upper Triassic Xujiahe Formation in Sichuan Basin, China and its Significance for Hydrocarbon Accumulation

Carbon isotope fractionation during shale gas transport: Mechanism, characterization and significance

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