“…A 30 mL column with 0.3 PV of residual oil contains 0.7 PV (9.5 mL) of 20 mM nitrate, which, upon complete reduction, would form 2.5 mL of N 2 gas at 30 C. In the absence of produced nitrite and residual nitrate, six repeated incubations (of which one was with 50 mM nitrate) would generate a calculated 18.8 mL of N 2 , which is sufficient to push out 1.53 mL of oil (a range of 1.00e2.07 mL) and 0.48 mL of water (a range of 0.45e0.5 mL) from 30 mL columns. Indeed, NRB were previously found to be capable of producing amounts of N 2 , which were sufficient for increasing pressure inside a model column/oil reservoir, leading to production of oil and/or water (Nuryadi et al, 2011). Microbial production of CO 2 in columns might also contribute to solution gas drive.…”