MODELING AND SIMULATION OF HYDROGEN STORAGE IN DEPLETED OIL RESERVOIRS UNDER BIOTIC CONDITIONS

Geological hydrogen storage can play a central role in enabling transition to a H₂-based economy, and reaching a net-zero carbon emission goal. The main limitation to the design, implementation, and management of geological hydrogen storage in depleted oil reservoirs is the lack of knowledge regarding the multiphase bio-geochemical reactive transport of H₂ in depleted oil reservoir and lack computer simulation programs that account for the multiphase bio-geochemical reactive transport of H₂. It is very well-known that, metabolically, H₂ can act as an electron donor and promote the activity of certain members of indigenous anaerobic microbial species, specifically, those coupling the use of H₂ as an electron donor with the utilization of CO₂ (methanogens) or sulfate (sulfate reducing bacteria) as electron acceptors for their growth. While a wide range of computer programs to simulate geological hydrogen storage are available, they do not account for the impact of microbiological and geochemical reactions on the multiphase bio-geochemical reactive transport of H₂ in depleted oil reservoirs. Here we present experimental results showing the feasibility of biogenic H₂ production and/or consumption in depleted oil reservoirs injected with CO₂, computer simulation results of the observed experimental results, as well as field-scale simulations of the fate of H₂ in depleted oil reservoirs under biotic conditions. Experiments were conducted using formation water and oil collected from the Stillwater oilfield. Simulations were done using CO2Bio. CO2Bio is a TOUGHREACT module we developed to simulate the multiphase bio-geochemical reactive transport of CO₂-CH₄-H₂-H₂S gas mixtures and brine in deep saline aquifers and depleted oil reservoirs under biotic conditions. The proposed framework will enable assessing the possibility of preventing the uptake of H₂ by indigenous microbial communities and enhancing the recovery of H₂ from geological hydrogen storage sites by pre-injecting CO₂ to reduce the pH to acidic pH and to work as cushion gas to facilitate its recovery.