Mechanisms of carbon isotopic fractionation in the process of natural gas generation: Geochemical evidence from thermal simulation experiment

PENG Weilong,LIU Quanyou,HU Guoyi,LYU Yue,ZHU Dongya,MENG Qingqiang,GUO Fengtao,WANG Ruoli

Table 2 Relative contents of gas components produced and carbon isotopic compositions of low mature coal sample from the Lower Permian Shanxi Formation in the eastern Ordos Basin.

Heating mode Temperature/ oC Main gas components /% Dryness coefficient/% δ13C/‰ CH4 C2H6 C3H8 iC4H10 nC4H10 iC5H12 nC5H12 H2 CO2 H2S CH4 C2H6 C3H8 iC4H10 nC4H10 Rapid heating 320 5.95 94.05 100.00 340 14.27 0.52 85.21 96.47 360 17.07 1.25 0.29 81.39 91.75 380 12.18 2.26 0.60 0.08 0.11 0.03 0.02 84.54 0.17 79.66 -32.9 400 21.89 4.80 0.84 0.05 0.06 72.37 79.22 -33.5 -28.0 -25.8 420 26.48 8.02 1.79 0.09 0.14 63.48 72.49 -34.8 -27.5 -25.4 -25.3 -25.4 440 36.88 10.50 2.58 0.15 0.23 0.02 0.02 49.61 73.20 -34.8 -26.2 -24.8 -25.8 -25.1 460 48.19 11.25 2.58 0.17 0.21 0.02 0.01 37.56 77.19 -33.9 -25.5 -23.9 -25.1 -24.0 480 51.72 9.88 2.02 0.11 0.14 0.64 35.49 80.97 -32.2 -24.6 -23.0 -23.6 -21.8 500 54.27 8.66 1.35 0.06 0.06 0.89 34.70 84.26 -31.2 -23.5 -20.9 525 64.82 6.47 0.47 0.02 28.21 90.30 -30.2 -20.3 -14.7 550 69.45 3.33 0.17 0.03 0.05 0.02 0.02 0.77 26.16 95.06 -27.9 -15.6 -18.8 575 74.04 1.00 0.81 24.15 98.66 -26.3 -9.0 600 78.72 0.44 0.85 19.99 99.45 -24.6 -12.4 625 81.64 0.27 0.92 17.18 99.67 -24.0 -14.9 650 -23.6 -17.5 Slow heating 320 6.68 0.63 0.14 92.55 89.67 340 11.07 1.37 0.22 87.34 87.43 -32.7 -28.9 -26.4 360 18.42 4.34 0.78 0.03 0.06 76.36 77.92 -34.8 -28.3 -25.4 380 22.55 6.74 1.53 0.07 0.15 0.01 0.02 68.93 72.57 -34.8 -27.5 -25.2 400 37.49 9.71 2.05 0.09 0.17 0.01 0.01 50.45 75.68 -35.5 -25.8 -24.1 420 42.35 9.54 2.06 0.11 0.19 0.02 0.01 45.72 78.03 -34.5 -24.7 -23.4 -25.3 -23.8 440 49.07 8.48 1.48 0.08 0.10 0.46 40.31 82.86 -32.5 -24.1 -23.2 460 56.82 7.06 0.83 0.05 0.03 0.45 34.77 87.70 -31.3 -22.5 -19.5 480 63.17 4.90 0.26 0.01 0.95 30.7 92.42 -29.6 -19.2 -13.2 500 69.30 2.67 0.04 0.66 27.32 96.23 -28.4 -14.1 525 78.83 0.97 0.01 0.73 19.46 98.77 -26.4 -8.3 550 82.11 0.32 0.02 0.98 16.57 99.59 -25.8 -13.0 575 85.50 0.28 1.36 12.74 0.12 99.68 -24.2 -14.9 600 87.51 0.23 1.72 10.40 0.14 99.73 -23.6 -16.0 625 89.27 0.14 2.01 8.58 99.84 -24.1 -18.9 650 -24.0 -23.7