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Exploration for commercially viable natural hydrogen accumulations within the Earth's crust, here compared to 'foraging' for wild food, holds promise. However, a potentially more effective strategy lies in the in situ artificial generation of hydrogen in natural underground reservoirs, akin to 'farming'. Both biotic and abiotic processes can be employed, converting introduced or indigenous components, gases, and nutrients into hydrogen. Through studying natural hydrogen-generating reactions, we can discern pathways for optimized engineering. Some reactions may be inherently slow, allowing for a 'seed and leave' methodology, where sites are infused with gases, nutrients, and specific bacterial strains, then left to gradually produce hydrogen. However, other reactions could offer quicker outcomes to harvest hydrogen. A crucial element of this strategy is our innovative concept of 'X' components-ranging from trace minerals to bioengineered microbes. These designed components enhance biotic and/or abiotic reactions and prove vital in accelerating hydrogen production. Drawing parallels with our ancestors' transition from hunter-gathering to agriculture, we propose a similar paradigm shift in the pursuit of hydrogen energy. As we transition towards a hydrogen-centric energy landscape, the amalgamation of geochemistry, advanced biology, and engineering emerges as a beacon, signalling a pathway towards a sustainable and transformative energy future.

Geological hydrogen storage in depleted gas fields represents a new technology to mitigate climate change. It comes with several research gaps, around hydrogen recovery, including the flow behavior of hydrogen gas in porous media. Here, we provide the first‐published comprehensive experimental study of unsteady state drainage relative permeability curves with H2‐Brine, on two different types of sandstones and a carbonate rock. We investigate the effect of pressure, brine salinity, and rock type on hydrogen flow behavior and compare it to that of CH4 and N2 at high‐pressure and high‐temperature conditions representative of potential geological storage sites. Finally, we use a history matching method for modeling relative permeability curves using the measured data within the experiments. Our results suggest that nitrogen can be used as a proxy gas for hydrogen to carry out multiphase fluid flow experiments, to provide the fundamental constitutive relationships necessary for large‐scale simulations of geological hydrogen storage. Plain Language Summary: Developing a hydrogen economy depends on safe and economically viable terawatt hour interseasonal storage and recovery of hydrogen around the world. As such, storage in geological formations is vital for transitioning to the hydrogen economy successfully. Here, we present a combined experimental and modeling study on the flow behavior of hydrogen in porous media at high‐pressure high‐temperature conditions representative of potential storage reservoirs. We investigate the effect of different influencing parameters and compare the flow behavior of hydrogen with other gases. This work provides essential relative permeability data for hydrogen under a range of conditions typical of hydrogen storage and extraction. Key Points: Drainage relative permeability is measured for H2‐brine at reservoir conditionsThe rocks' effective porosity has the most evident impact on H2‐brine relative permeabilityN2 gas can be used as a safer proxy for hydrogen to undertake fluid flow experiments [ABSTRACT FROM AUTHOR]

The use of hydrogen (H2) as a substitute for fossil fuel, which accounts for the majority of the world's energy, is environmentally the most benign option for the reduction of CO2 emissions. This will require gigawatt-scale storage systems and as such, H2 storage in porous rocks in the subsurface will be required. Accurate estimation of the thermodynamic and transport properties of H2 mixed with other gases found within the storage system is therefore essential for the efficient design for the processes involved in this system chain. In this study, we used the established and regarded GERG-2008 Equation of State (EoS) and SuperTRAPP model to predict the thermo-physical properties of H2 mixed with CH4, N2, CO2, and a typical natural gas from the North-Sea. The data covers a wide range of mole fraction of H2 (10–90 Mole%), pressures (0.01–100 MPa), and temperatures (200–500 K) with high accuracy and precision. Moreover, to increase ease of access to the data, a user-friendly software (H2Themobank) is developed and made publicly available. Measurement(s) thermodynamic property • transport property Technology Type(s) computational modeling technique Factor Type(s) mole fraction of H2 • pressure • temperature Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12554804 [ABSTRACT FROM AUTHOR]

Hydrogen can act as an energy store to balance supply and demand in the renewable energy sector. Hydrogen storage in subsurface porous media could deliver high storage capacities but the volume of recoverable hydrogen is unknown. We imaged the displacement and capillary trapping of hydrogen by brine in a Clashach sandstone core at 2–7 MPa pore fluid pressure using X-ray computed microtomography. Hydrogen saturation obtained during drainage at capillary numbers of <10−7 was ∼50% of the pore volume and independent of the pore fluid pressure. Hydrogen recovery during secondary imbibition at a capillary number of 2.4 × 10−6 systematically decreased with pressure, with 80%, 78% and 57% of the initial hydrogen recovered at 2, 5 and 7 MPa, respectively. Injection of brine at increasing capillary numbers up to 9.4 × 10−6 increased hydrogen recovery. Based on these results, we recommend more shallow, lower pressure sites for future hydrogen storage operations in porous media. • Hydrogen injectivity and recovery in rock is imaged with x-ray computed micro-CT. • Hydrogen recovery decreases with increasing reservoir depth. • Hydrogen recovery increases with increasing brine flow rate. • Hydrogen trapping occurs via snap-off processes. • Nitrogen is a poor proxy for hydrogen. [ABSTRACT FROM AUTHOR]

• Critical role of geochemical interactions between hydrogen and host sandstone. • The influence of clay composition on hydrogen-sandstone interaction is examined. • 75 days of injection at 1500 psi and 75 °C into Berea and Bandera gray sandstone cores are used for assessment. • Microcomputed tomography is utilized to evaluate changes in pore structure. • The results indicate minimal alteration in porosity and mineral content. Hydrogen holds promise as a clean energy alternative, crucial for achieving global decarbonization goals and net-zero carbon emissions. Its low volumetric energy density necessitates underground storage in sandstone formations to maintain year-round supply. The efficacy of such storage hinges on the geochemical interplay between hydrogen and the host sandstone. Despite the slow reaction rates in sandstone, the influence of its clay composition on hydrogen interaction remains underexplored. In this study, we specifically investigate the geochemical interactions of hydrogen with clay-bearing sandstone formations under controlled conditions, simulating storage scenarios. This study evaluates the impact of clay on hydrogen-sandstone geochemistry after 75 days of injection at 1500 psi and 75 °C into Berea and Bandera gray sandstone cores, utilizing microcomputed tomography to assess changes in pore structure. Our results reveal that, even in sandstones with high clay content, there is negligible alteration in porosity and mineral content, as well as minimal clay and quartz dissolution or expansion over storage time, indicating stability in these formations. These findings provide crucial insights for selecting suitable geological formations for hydrogen storage, supporting the global shift towards sustainable energy systems Our study contributes to the global efforts in decarbonization by providing essential guidance on the feasibility of using clay-bearing sandstone formations for efficient and sustainable hydrogen storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Risk categorization based on a novel collection of microbial growth constraints. • No and low microbial risk depleted gas fields on the UK continental shelf revealed. • Alignment with wind farms and pipelines highlights fields within Southern North Sea. • Methodology applicable to any underground porous rock system globally. Geological hydrogen storage, e.g. in depleted gas fields (DGF), can overcome imbalances between supply and demand in the renewable energy sector and facilitate the transition to a low carbon emissions society. A range of subsurface microorganisms utilise hydrogen, which may have important implications for hydrogen recovery, clogging and corrosion. We gathered temperature and salinity data for 75 DGF on the UK continental shelf and mapped their suitability for hydrogen storage in terms of the risk of adverse microbial effects, based on a novel collection of microbial growth constraints. Data on wind and solar operational capacities as well as offshore gas and condensate pipeline infrastructure were overlaid on the microbial risk categorization to optimize geographical centers of green hydrogen production, transport infrastructure and underground storage. We recommend storing hydrogen in 9 DGF that are at no microbial risk due to temperatures > 122 °C, or in the 35 low-risk DGF with temperatures > 90 °C. We recommend against utilising high-risk DGF with temperatures < 55 °C (9 DGF). Alignment with centers for renewable energy production and out-of-use pipelines suitable for repurposing to transport hydrogen suggests that no-risk and low-risk DGF in the Southern North Sea are the most suitable candidates for hydrogen storage. Our results advise site selection choices in geological hydrogen storage in the UK. Our methodology is applicable to any underground porous rock system globally. [ABSTRACT FROM AUTHOR]

Subsurface storage of hydrogen, e.g. in depleted oil and gas fields (DOGF), is suggested as a means to overcome imbalances between supply and demand in the renewable energy sector. However, hydrogen is an electron donor for subsurface microbial processes, which may have important implications for hydrogen recovery, gas injectivity and corrosion. Here, we review the controls on the three major hydrogen consuming processes in the subsurface, methanogenesis, homoacetogenesis, and sulfate reduction, as a basis to estimate the risk for microbial growth in geological hydrogen storage. Evaluating our data on 42 DOGF showed that five of the fields may be considered sterile with respect to hydrogen-consuming microorganisms due to temperatures >122 °C. Only six DOGF can sustain all of the hydrogen consuming processes, due to either temperature, salinity or pressure constraints in the remaining fields. We calculated a potential microbial growth in the order of 1–17*107 cells ml−1 for DOGF with favorable conditions for microbial growth, reached after 0.1–19 days for growing cells and 0.2–6.6 years for resting cells. The associated hydrogen consumption is negligible to small (<0.01–3.2% of the stored hydrogen). Our results can help inform decisions about where hydrogen will be stored in the future. [Display omitted] • Review of the most important hydrogen-oxidizing microorganisms in the underground. • Elucidation of the growth criteria for 518 strains of the major hydrogen-oxidizers. • Screening of 42 depleted oil and gas fields (DOGF) for possible microbial growth. • Calculation of the microbial growth and hydrogen consumption in DOGF. [ABSTRACT FROM AUTHOR]