Open AccessNovel Coalbed Methane (CBM) Origin Analysis and Source Apportionment Method Based on Carbon Isotope Ratio Using Infrared Dual‐Wavelength Laser Absorption Spectroscopy
Author(s) -
Zhang Zhirong,
Sun Pengshuai,
Li Zhe,
Xia Hua,
Cui Xiaojuan,
Pang Tao,
Wu Bian,
Guo Qiang,
Shu Chimin,
Dong Fengzhong
Publication year - 2018
Publication title -
earth and space science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.843
H-Index - 23
ISSN - 2333-5084
DOI - 10.1029/2018ea000437
Subject(s) - coalbed methane , methane , spectroscopy , absorption (acoustics) , isotopes of carbon , carbon fibers , analytical chemistry (journal) , infrared spectroscopy , coal , environmental science , absorption spectroscopy , laser , chemistry , mineralogy , materials science , environmental chemistry , total organic carbon , coal mining , optics , physics , organic chemistry , quantum mechanics , composite number , composite material
We report the application of an infrared dual‐wavelength laser absorption spectroscopy system, which combines tunable diode laser absorption spectroscopy and wavelength modulation integrated cavity output spectroscopy technologies based on two spectroscopic sources operating at 6,029 and 2,310 cm −1 , to simultaneously measure the gas concentrations (CH 4 and CO 2 ) and carbon isotopic signatures ( 13 C and 12 C) in coalbed methane. The Allan variance is used to analyze the optimum mean time ( t ) and the standard deviation ( SD ), with t = 450 s, SD = 0.41‰ for 13 CH 4 monitoring and t = 70 s, SD = 0.17‰ for 13 CO 2 monitoring. Furthermore, 47 groups of coalbed methane samples collected from the Huaibei‐Qidong coal mine seam are analyzed based on the measured results for carbon isotopes and geophysical geochemistry. The δ 13 CH 4 values of the Qidong coal mine fall between −44.57‰ and −61.57‰, and the δ 13 CO 2 values fall between −21.65‰ and −17.06‰. The genetic types of methane may be divided into biogenic gas, thermogenic gas, and mixture gas. Carbon dioxide may be derived from coal pyrolysis, and it also has the characteristics of carbon‐isotope changes of organic genetic gas. The new approach for analyzing rapid genetic types, methane migration pathways, gas disaster source warning, and coal chemistry studies is expected to be further studied in the future.