In-situ hydrogen production from natural gas reservoirs and gas separation by graphite packing: Process simulation and experimental study

The generation of hydrogen in-situ from hydrocarbon reservoirs has emerged as a carbon neutral technology for fossil fuel-based hydrogen production. This technology has been extensively investigated for heavy oil reservoirs through in-situ combustion gasification. This study proposes in-situ hydrogen generation from depleted gas reservoirs and assess graphite gravel packing for selective hydrogen production with underground carbon storage. The viability of this hydrogen generation process was accessed through process simulation, followed by experimental investigation and molecular simulation of the selective production of hydrogen through graphite. Equilibrium and kinetic models reproduced measured effluent fractions, confirming their reliability. The simulation outcomes reveal that higher temperature and steam-to-carbon ratio increase hydrogen yield/purity, whereas high pressure favors methanation. This necessitates elevated temperatures beyond the usual reaction temperature under reservoir conditions. Longer residence time and judicious catalyst loading improve conversion while limiting diminishing returns. Adiabatic simulation yields lower hydrogen purity than isothermal but better reflects field behavior. Reservoir mineralogy governs outcomes as quartz-rich rocks inhibit hydrogen production by steam reforming, while clays/feldspars reported elsewhere can be catalytic. The experimental results showed that graphite can be used as gravel pack in the production well to produce hydrogen and retain carbon dioxide underground. Literature report indicates that high compaction can further enhance separation significantly reducing the carbon emission associated with hydrogen production from fossil fuels.