Table 1 Thermodynamic parameters and Gibbs free energies of three reactions in the control and CO2-injected microcosms.

From: Carbon dioxide concentration dictates alternative methanogenic pathways in oil reservoirs

     

ΔG55, 50 (kJ)†

Reaction

ΔH o (kJ)

ΔG o (kJ)

ΔGo55, 1 (kJ)*

ΔGo55, 50 (kJ)*

Control

CO 2 -injected

Acetoclastic methanogenesis (CH3COO−+H+→CH4+CO2)

17.7

−75.8

−85.2

−85.0

−22.4

−17.1

Acetate oxidation (CH3COO−+H++2H2O →4H2+2CO2)

270.6

55.0

33.3

33.8

−6.3

6.1

Hydrogenotrophic methanogenesis (4H2+CO2→CH4+2H2O)

−252.9

−130.8

−118.5

−118.8

−16.1

−23.1

  1. *The Gibbs free energies, ΔGo55, 1 and ΔGo55, 50, were calculated under the conditions at 55 °C and 1 atm, and at 55 °C and 50 atm, respectively.
  2. †The Gibbs free energies in the control and CO2-injected microcosms were calculated using actual conditions in the unlabeled microcosms at day 116 and 77 of the control and CO2-injected microcosms, respectively, at 55 °C and 50 atm.
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