Economic and Environmental Geology

Table. 2.

Table. 2.

Molecular compositions and carbon isotope ratios of ethane (δ13CC2) and carbon dioxide (δ13CCO2) of coalbed gases in AA-1 core samples from the Asem-Asem Basin, southeast Kalimantan, Indonesia

Depth (mbs) Molecular composition (mol %) Stable isotopes (‰) CDMI (%)
C1 C2 C3 C4+5 CO2 N2 O2 CO δ13CC2 δ13CCO2
505.90∼506.60 1.04 0.0598 0.0252 0.0014 6.71 84.25 6.86 0.067 -32.8 -7.3 86.6
507.10∼507.40 0.972 0.111 0.0276 0.0022 2.37 91.44 3.91 0.100 -31.2 -8.2 70.9
508.40∼508.50 6.12 0.293 0.0784 0.0029 18.31 72.04 2.27 nd -31.5 -6.2 74.9
514.35∼514.67 4.95 0.244 0.0573 0.0026 16.34 75.41 2.08 nd -31.8 -6.2 76.7
516.80∼517.10 3.70 0.213 0.0459 0.0022 5.01 84.57 5.46 nd nd -7.0 57.5
517.10∼517.37 0.939 0.0718 0.0214 0.0013 2.25 91.12 4.50 0.049 nd -8.6 70.6

CDMI; carbon dioxide-methane index ([CO2/(CH4+CO2)]*100(%), Kotarba and Rice, 2001). mbs; meter below surface.

Econ. Environ. Geol. 2022;55:261-71 https://doi.org/10.9719/EEG.2022.55.3.261
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