Use of iron-rich scavenging reservoirs to unlock stranded sour hydrocarbons with amber hydrogen byproduct

Hydrogen sulfide (H 2 S) is a relatively common component in hydrocarbon fields, where it may be mixed with hydrocarbon oil or gas in proportions up to 50% or more. Such hydrocarbons are often described as ‘sour’. The H 2 S primarily originates from thermochemical sulfate reduction associated with evaporites, though biogenic pathways may apply in some cases. Hydrocarbon fields with the highest concentrations of H 2 S often remain undeveloped, representing already-discovered resources that could support the transition towards a lower-carbon economy. Meanwhile, hydrogen — recognized as a critical element of the energy transition — can be obtained from H 2 S currently by several energy consuming processes. A new subsurface engineering concept introduced here combines the rehabilitation of stranded sour hydrocarbon resources via H 2 S removal with the production of potentially economic amounts of hydrogen. The proposed approach removes H 2 S from the hydrocarbons as they are passed through a subsurface iron-rich ‘scavenging’ reservoir. Reactions between the sour hydrocarbons and the iron minerals in this reservoir convert H 2 S to solid iron sulfide (pyrite) releasing hydrogen gas during the process. Sweetened hydrocarbons, hydrogen, or both, can then be produced. Subsurface removal of H 2 S and sequestering of sulfur from known stranded hydrocarbons avoids the cost and risk of surface-based H 2 S facilities as well as exploration costs for new hydrocarbons in pristine locations. Hydrogen produced from H 2 S in this way is called here ‘amber hydrogen’, an addition to the hydrogen color spectrum that can also be applied to hydrogen produced from H 2 S by any method.