LAUSR

Abstract A new TOUGHREACT module named CO2Bio is introduced to simulate geological carbon storage (GCS) under biotic conditions. CO2Bio is developed by incorporating into TOUGHREACT an expanded thermodynamic model capable of predicting the mutual solubility of CO2-CH4-H2S-H2 gas mixtures and brine. Simple but robust thermophysical correlations are adopted in CO2Bio to calculate density, viscosity and enthalpy of CO2-CH4-H2S-H2 gas mixtures. CO2Bio can predict the kinetic microbial production and/or consumption of CO2, CH4, H2S, and H2 gases, and the multiphase flow of CO2-CH4-H2S-H2 gas mixtures and brine at deep geological formation conditions. The multiphase flow capabilities of CO2Bio are verified by comparing its simulation results with other reliable multiphase simulation programs including the ECO2N module of TOUGHREACT, the EOS7C module of TOUGH2, and CMG-GEM©. Simulated scenarios include injection of CO2 into a radial infinite acting saline aquifer, extraction of dissolved CH4 from CH4-saturated water by CO2 injection, and injection of CO2 mixed with H2S as an impurity into a saline aquifer. To verify the field-scale applicability of TOUGHREACT-CO2Bio, we conducted simulations for alternate injection of CO2 and brine into the Cushing-Drumright oil reservoir of Oklahoma where the supply of nutrients such as protein-rich matter was assumed to result in the stimulation of microbial production of H2 and CH4 from the degradation of n-alkanes. Our simulation results confirm that TOUGHREACT-CO2Bio is capable of predicting the multiphase flow of CO2-CH4-H2S-H2 gas mixtures and brine.