TY - JOUR
T1 - Position-specific carbon and hydrogen isotopic compositions of propane from natural gases with quantitative NMR
AU - Liu, Changjie
AU - McGovern, Gregory P.
AU - Liu, Peng
AU - Zhao, Heng
AU - Horita, Juske
N1 - Publisher Copyright:
© 2018 Elsevier B.V.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/7/5
Y1 - 2018/7/5
N2 - Position-specific isotope compositions of light hydrocarbons are expected to provide valuable information on their formation and migration-degradation processes. Here we present a high-accuracy and high-precision (≤±10 and ≤±1‰ for 2H and 13C isotope compositions, respectively) method to determine position-specific hydrogen and carbon isotope compositions of propane from natural gases with quantitative NMR. Customized, light-weight high-pressure sapphire NMR cells were developed for liquefied propane samples. Precision and accuracy of our technique were demonstrated using 13C-labeled compounds, neat samples of C3-C5 with natural isotope abundances, and inter-laboratory comparison of a C7 sample. To determine position-specific isotope compositions of propane from natural gas samples, a method was developed to collect and purify large amount (~6.8 mmol) of propane, using a variable-temperature cold trap. A test with a synthetic sample of natural gas mixture indicates that little isotope fractionation occurred during the propane separation and purification from natural gas mixtures. For the first time, high-precision and high accuracy data are reported of position-specific carbon and hydrogen isotope compositions of propane from different sources, including conventional and unconventional petroleum reservoirs. Preliminary results show that position-specific isotope fractionations between the center and terminal sites of propane vary widely for the different sources. Position-specific isotope compositions of propane have the potential to improve our understanding on the origins, migration and degradation processes of natural gas and hydrocarbons in general.
AB - Position-specific isotope compositions of light hydrocarbons are expected to provide valuable information on their formation and migration-degradation processes. Here we present a high-accuracy and high-precision (≤±10 and ≤±1‰ for 2H and 13C isotope compositions, respectively) method to determine position-specific hydrogen and carbon isotope compositions of propane from natural gases with quantitative NMR. Customized, light-weight high-pressure sapphire NMR cells were developed for liquefied propane samples. Precision and accuracy of our technique were demonstrated using 13C-labeled compounds, neat samples of C3-C5 with natural isotope abundances, and inter-laboratory comparison of a C7 sample. To determine position-specific isotope compositions of propane from natural gas samples, a method was developed to collect and purify large amount (~6.8 mmol) of propane, using a variable-temperature cold trap. A test with a synthetic sample of natural gas mixture indicates that little isotope fractionation occurred during the propane separation and purification from natural gas mixtures. For the first time, high-precision and high accuracy data are reported of position-specific carbon and hydrogen isotope compositions of propane from different sources, including conventional and unconventional petroleum reservoirs. Preliminary results show that position-specific isotope fractionations between the center and terminal sites of propane vary widely for the different sources. Position-specific isotope compositions of propane have the potential to improve our understanding on the origins, migration and degradation processes of natural gas and hydrocarbons in general.
KW - Natural gas
KW - Position-specific isotope analysis
KW - Propane
KW - Quantitative NMR
UR - http://www.scopus.com/inward/record.url?scp=85047554202&partnerID=8YFLogxK
U2 - 10.1016/j.chemgeo.2018.05.011
DO - 10.1016/j.chemgeo.2018.05.011
M3 - Article
AN - SCOPUS:85047554202
VL - 491
SP - 14
EP - 26
JO - Chemical Geology
JF - Chemical Geology
SN - 0009-2541
ER -