Geochemical characteristics and implications of shale gas from the Longmaxi Formation, Sichuan Basin, China
Gas geochemical analysis was conducted on the shale gas from the Longmaxi Formation in the Weiyuan-Changning areas, Sichuan Basin, China. Chemical composition was measured using an integrated method of gas chromatography combined with mass spectrometry. The results show that the Longmaxi shale gas,...
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doaj-4c7db00597a64189bddcd9b44929c75e2020-11-24T20:43:11ZengElsevierJournal of Natural Gas Geoscience2468-256X2016-04-011213113810.1016/j.jnggs.2016.05.001Geochemical characteristics and implications of shale gas from the Longmaxi Formation, Sichuan Basin, ChinaChunhui Cao0Zonggang Lv1Liwu Li2Li Du3Key Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, ChinaShu'nan Gas-mine Field, PetroChina Southwest Oil & Gas Field Branch Company, Luzhou 648000, ChinaKey Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, ChinaKey Laboratory of Petroleum Resources, Gansu Province/Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Lanzhou 730000, ChinaGas geochemical analysis was conducted on the shale gas from the Longmaxi Formation in the Weiyuan-Changning areas, Sichuan Basin, China. Chemical composition was measured using an integrated method of gas chromatography combined with mass spectrometry. The results show that the Longmaxi shale gas, after hydraulic fracturing, is primarily dominated by methane (94.0%–98.6%) with low humidity (0.3%–0.6%) and minor non-hydrocarbon gasses which are primarily comprised of CO2, N2, as well as trace He. δ13CCO2 = −2.5‰−6.0‰3He/4He = 0.01–0.03Ra.The shale gas in the Weiyuan and Changning areas display carbon isotopes reversal pattern with a carbon number (δ13C1 > δ13C2) and distinct carbon isotopic composition. The shale gas from the Weiyuan pilot has heavier carbon isotopic compositions for methane (δ13C1: from −34.5‰ to −36.8‰), ethane (δ13C2: −37.6‰ to −41.9‰), and CO2 (δ13CCO2: −4.5‰ to −6.0‰) than those in the Changning pilot (δ13C1: −27.2‰ to −27.3‰, δ13C2: −33.7‰ to −34.1‰, δ13CCO2: −2.5‰ to −4.6‰). The Longmaxi shale was thermally high and the organic matter was in over mature stage with good sealing conditions. The shale gas, after hydraulic fracturing, could possibly originate from the thermal decomposition of kerogen and the secondary cracking of liquid hydrocarbons which caused the reversal pattern of carbon isotopes. Some CO2 could be derived from the decomposition of carbonate. The difference in carbon isotopes between the Weiyuan and Changning areas could be derived from the different mixing proportion of gas from the secondary cracking of liquid hydrocarbons caused by specific geological and geochemical conditions.http://www.sciencedirect.com/science/article/pii/S2468256X16300104Stable isotopeChemical compositionShale gasLongmaxi formationSichuan basin |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Chunhui Cao Zonggang Lv Liwu Li Li Du |
spellingShingle |
Chunhui Cao Zonggang Lv Liwu Li Li Du Geochemical characteristics and implications of shale gas from the Longmaxi Formation, Sichuan Basin, China Journal of Natural Gas Geoscience Stable isotope Chemical composition Shale gas Longmaxi formation Sichuan basin |
author_facet |
Chunhui Cao Zonggang Lv Liwu Li Li Du |
author_sort |
Chunhui Cao |
title |
Geochemical characteristics and implications of shale gas from the Longmaxi Formation, Sichuan Basin, China |
title_short |
Geochemical characteristics and implications of shale gas from the Longmaxi Formation, Sichuan Basin, China |
title_full |
Geochemical characteristics and implications of shale gas from the Longmaxi Formation, Sichuan Basin, China |
title_fullStr |
Geochemical characteristics and implications of shale gas from the Longmaxi Formation, Sichuan Basin, China |
title_full_unstemmed |
Geochemical characteristics and implications of shale gas from the Longmaxi Formation, Sichuan Basin, China |
title_sort |
geochemical characteristics and implications of shale gas from the longmaxi formation, sichuan basin, china |
publisher |
Elsevier |
series |
Journal of Natural Gas Geoscience |
issn |
2468-256X |
publishDate |
2016-04-01 |
description |
Gas geochemical analysis was conducted on the shale gas from the Longmaxi Formation in the Weiyuan-Changning areas, Sichuan Basin, China. Chemical composition was measured using an integrated method of gas chromatography combined with mass spectrometry. The results show that the Longmaxi shale gas, after hydraulic fracturing, is primarily dominated by methane (94.0%–98.6%) with low humidity (0.3%–0.6%) and minor non-hydrocarbon gasses which are primarily comprised of CO2, N2, as well as trace He. δ13CCO2 = −2.5‰−6.0‰3He/4He = 0.01–0.03Ra.The shale gas in the Weiyuan and Changning areas display carbon isotopes reversal pattern with a carbon number (δ13C1 > δ13C2) and distinct carbon isotopic composition. The shale gas from the Weiyuan pilot has heavier carbon isotopic compositions for methane (δ13C1: from −34.5‰ to −36.8‰), ethane (δ13C2: −37.6‰ to −41.9‰), and CO2 (δ13CCO2: −4.5‰ to −6.0‰) than those in the Changning pilot (δ13C1: −27.2‰ to −27.3‰, δ13C2: −33.7‰ to −34.1‰, δ13CCO2: −2.5‰ to −4.6‰). The Longmaxi shale was thermally high and the organic matter was in over mature stage with good sealing conditions. The shale gas, after hydraulic fracturing, could possibly originate from the thermal decomposition of kerogen and the secondary cracking of liquid hydrocarbons which caused the reversal pattern of carbon isotopes. Some CO2 could be derived from the decomposition of carbonate. The difference in carbon isotopes between the Weiyuan and Changning areas could be derived from the different mixing proportion of gas from the secondary cracking of liquid hydrocarbons caused by specific geological and geochemical conditions. |
topic |
Stable isotope Chemical composition Shale gas Longmaxi formation Sichuan basin |
url |
http://www.sciencedirect.com/science/article/pii/S2468256X16300104 |
work_keys_str_mv |
AT chunhuicao geochemicalcharacteristicsandimplicationsofshalegasfromthelongmaxiformationsichuanbasinchina AT zongganglv geochemicalcharacteristicsandimplicationsofshalegasfromthelongmaxiformationsichuanbasinchina AT liwuli geochemicalcharacteristicsandimplicationsofshalegasfromthelongmaxiformationsichuanbasinchina AT lidu geochemicalcharacteristicsandimplicationsofshalegasfromthelongmaxiformationsichuanbasinchina |
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