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We found that supercritical CO2 and the availability of protein-rich matter in depleted oil reservoirs can result in the biogenic production of H2 from oil hydrocarbons by indigenous microbial communities. Our experimental results support the hypothesis that a decrease in pH to acidic levels due to the dissolution of supercritical CO2 into the formation water and availability of protein-rich matter favors the activity of H2-producing microbial communities over the activity of H2-using microbial communities. To determine where, when, and how much H2 could be produced in a depleted oil reservoir injected with CO2 and produced water (PW) supplied with protein-rich matter, we simulated the biogenic production of H2 for the Morrow B sandstone reservoir. Simulations were conducted using CO2Bio, a program developed to simulate the multiphase bio-geochemical reactive transport of CO2-CH4-H2-H2S gases in geological carbon storage (GCS) sites. The microbiological capabilities of CO2Bio are validated against batch reaction experimental results. Our field-scale simulation results indicate that 154 – 1673 kg of H2 could be produced after 100 days of CO2 and PW co-injection into a single well of radial flow, and that sandstone reservoirs are more suitable than carbonate reservoirs to produce H2 from dissolved hydrocarbons. Based on the obtained experimental and simulation results, we propose a new H2 production method that couples GCS and PW disposal in depleted oil reservoirs to attenuate environmental and energy issues related to global warming derived from atmospheric pollution with CO2, risk of freshwater resources contamination with PW, and depletion of energy resources.