In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China

Abstract We re-evaluate the Raman spectroscopic quantification of the molar ratio and pressure for CH4–CO2 mixtures. Firstly, the Raman quantification factors of CH4 and CO2 increase with rising pressure at room temperature, indicating that Raman quantification of CH4/CO2 molar ratio can be applied...

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Autores principales:	Ye Qiu, Xiao-Lin Wang, Xian Liu, Jian Cao, Yi-Feng Liu, Bin-Bin Xi, Wan-Lu Gao
Formato:	article
Lenguaje:	EN
Publicado:	KeAi Communications Co., Ltd. 2019
Materias:	Raman spectroscopy Molar ratio Fluid pressure CO2–CH4 mixture Fluid inclusion Paleo-overpressure Science Q Petrology QE420-499
Acceso en línea:	https://doaj.org/article/c41de03f951043e1abc7f83b7ef0d56d
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spelling	oai:doaj.org-article:c41de03f951043e1abc7f83b7ef0d56d2021-12-02T15:17:41ZIn situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China10.1007/s12182-019-00395-z1672-51071995-8226https://doaj.org/article/c41de03f951043e1abc7f83b7ef0d56d2019-12-01T00:00:00Zhttps://doi.org/10.1007/s12182-019-00395-zhttps://doaj.org/toc/1672-5107https://doaj.org/toc/1995-8226Abstract We re-evaluate the Raman spectroscopic quantification of the molar ratio and pressure for CH4–CO2 mixtures. Firstly, the Raman quantification factors of CH4 and CO2 increase with rising pressure at room temperature, indicating that Raman quantification of CH4/CO2 molar ratio can be applied to those fluid inclusions (FIs) with high internal pressure (i.e., > 15 MPa). Secondly, the v 1(CH4) peak position shifts to lower wavenumber with increasing pressure at constant temperature, confirming that the v 1(CH4) peak position can be used to calculate the fluid pressure. However, this method should be carefully calibrated before applying to FI analyses because large discrepancies exist among the reported v 1(CH4)-P curves, especially in the high-pressure range. These calibrations are applied to CH4-rich FIs in quartz veins of the Silurian Longmaxi black shales in southern Sichuan Basin. The vapor phases of these FIs are mainly composed of CH4 and minor CO2, with CO2 molar fractions from 4.4% to 7.4%. The pressure of single-phase gas FI ranges from 103.65 to 128.35 MPa at room temperature, which is higher than previously reported. Thermodynamic calculations supported the presence of extremely high-pressure CH4-saturated fluid (218.03–256.82 MPa at 200 °C), which may be responsible for the expulsion of CH4 to adjacent reservoirs.Ye QiuXiao-Lin WangXian LiuJian CaoYi-Feng LiuBin-Bin XiWan-Lu GaoKeAi Communications Co., Ltd.articleRaman spectroscopyMolar ratioFluid pressureCO2–CH4 mixtureFluid inclusionPaleo-overpressureScienceQPetrologyQE420-499ENPetroleum Science, Vol 17, Iss 1, Pp 23-35 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	Raman spectroscopy Molar ratio Fluid pressure CO2–CH4 mixture Fluid inclusion Paleo-overpressure Science Q Petrology QE420-499
spellingShingle	Raman spectroscopy Molar ratio Fluid pressure CO2–CH4 mixture Fluid inclusion Paleo-overpressure Science Q Petrology QE420-499 Ye Qiu Xiao-Lin Wang Xian Liu Jian Cao Yi-Feng Liu Bin-Bin Xi Wan-Lu Gao In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China
description	Abstract We re-evaluate the Raman spectroscopic quantification of the molar ratio and pressure for CH4–CO2 mixtures. Firstly, the Raman quantification factors of CH4 and CO2 increase with rising pressure at room temperature, indicating that Raman quantification of CH4/CO2 molar ratio can be applied to those fluid inclusions (FIs) with high internal pressure (i.e., > 15 MPa). Secondly, the v 1(CH4) peak position shifts to lower wavenumber with increasing pressure at constant temperature, confirming that the v 1(CH4) peak position can be used to calculate the fluid pressure. However, this method should be carefully calibrated before applying to FI analyses because large discrepancies exist among the reported v 1(CH4)-P curves, especially in the high-pressure range. These calibrations are applied to CH4-rich FIs in quartz veins of the Silurian Longmaxi black shales in southern Sichuan Basin. The vapor phases of these FIs are mainly composed of CH4 and minor CO2, with CO2 molar fractions from 4.4% to 7.4%. The pressure of single-phase gas FI ranges from 103.65 to 128.35 MPa at room temperature, which is higher than previously reported. Thermodynamic calculations supported the presence of extremely high-pressure CH4-saturated fluid (218.03–256.82 MPa at 200 °C), which may be responsible for the expulsion of CH4 to adjacent reservoirs.
format	article
author	Ye Qiu Xiao-Lin Wang Xian Liu Jian Cao Yi-Feng Liu Bin-Bin Xi Wan-Lu Gao
author_facet	Ye Qiu Xiao-Lin Wang Xian Liu Jian Cao Yi-Feng Liu Bin-Bin Xi Wan-Lu Gao
author_sort	Ye Qiu
title	In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China
title_short	In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China
title_full	In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China
title_fullStr	In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China
title_full_unstemmed	In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China
title_sort	in situ raman spectroscopic quantification of ch4–co2 mixture: application to fluid inclusions hosted in quartz veins from the longmaxi formation shales in sichuan basin, southwestern china
publisher	KeAi Communications Co., Ltd.
publishDate	2019
url	https://doaj.org/article/c41de03f951043e1abc7f83b7ef0d56d
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In situ Raman spectroscopic quantification of CH4–CO2 mixture: application to fluid inclusions hosted in quartz veins from the Longmaxi Formation shales in Sichuan Basin, southwestern China

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