Migration of Natural Hydrogen from Deep-Seated Sources in the São Francisco Basin, Brazil

Hydrogen production, storage, and transportation: recent advances

One such technology is hydrogen-based which utilizes hydrogen to generate energy without emission of greenhouse gases. The advantage of such technology is the fact that the only by-product is water. Efficient storage is crucial for the practical application of hydrogen. There are several techniques to store hydrogen, each with certain advantages and disadvantages. In gaseous hydrogen storage, hydrogen gas is compressed and stored at high pressures, requiring robust and expensive pressure vessels. In liquid hydrogen storage, hydrogen is cooled to extremely low temperatures and stored as a liquid, which is energy-intensive. Researchers are exploring advanced materials for hydrogen storage, including metal hydrides, carbon-based materials, metal-organic frameworks (MOFs), and nanomaterials. These materials aim to enhance storage capacity, kinetics, and safety. The hydrogen economy envisions hydrogen as a clean energy carrier, utilized in various sectors like transportation, industry, and power generation. It can contribute to decarbonizing sectors that are challenging to electrify directly. Hydrogen can play a role in a circular economy by facilitating energy storage, supporting intermittent renewable sources, and enabling the production of synthetic fuels and chemicals. The circular economy concept promotes the recycling and reuse of materials, aligning with sustainable development goals. Hydrogen availability depends on the method of production. While it is abundant in nature, obtaining it in a clean and sustainable manner is crucial. The efficiency of hydrogen production and utilization varies among methods, with electrolysis being a cleaner but less efficient process compared to other conventional methods. Chemisorption and physisorption methods aim to enhance storage capacity and control the release of hydrogen. There are various viable options that are being explored to solve these challenges, with one option being the use of a multilayer film of advanced metals. This work provides an overview of hydrogen economy as a green and sustainable energy system for the foreseeable future, hydrogen production methods, hydrogen storage systems and mechanisms including their advantages and disadvantages, and the promising storage system for the future. In summary, hydrogen holds great promise as a clean energy carrier, and ongoing research and technological advancements are addressing challenges related to production, storage, and utilization, bringing us closer to a sustainable hydrogen economy.

Characterization of the spontaneously recharging natural hydrogen reservoirs of Bourakebougou in Mali

In today's race to find ways to produce cheap and green hydrogen, the natural hydrogen wells in Bourakebougou offer a promising solution and are a good example of how H₂ can be produced in the natural environment. Not only has one well been successfully exploited to generate electricity for the local village, but twenty-four other exploratory boreholes have also demonstrated the presence of natural H₂ in the surrounding area. The Bourakebougou H₂ field offers a unique opportunity for geoscientists to determine the key characteristics of natural hydrogen reservoirs. This paper presents the coring, logging, and geochemistry studies that were performed to better characterize the nature of the Bourakebougou H₂-bearing reservoirs. The shallowest main reservoir, in which there is the highest content of H₂, is made of dolomitic carbonate (Neoproterozoic cap carbonate). These carbonates are largely karstified and show a high degree of heterogeneity in porosity (0.21-14.32%). Based on the analysis of the drilling imagery of the carbonated reservoirs, the accumulation of hydrogen occurs in the karst (void) representing a secondary porosity in the rock matrix. Other reservoirs, especially the deepest ones, are porous sandstone rocks with much more homogeneous porosities (4.52-6.37%) compared to the massive carbonates. For the wells analysed, the neutron tool reacted in a specific way when there is the presence of hydrogen. Hence, it stands out as being the primary tool to detect the presence of natural hydrogen beyond simple gas logging. When comparing a H₂ reservoir system to classical oil and gas reservoir systems, the results show that the hydrogen reservoir is a dynamic system that is progressively recharged in H₂-rich gas at the production timescale.

Can Weathering of Banded Iron Formations Generate Natural Hydrogen? Evidence from Australia, Brazil and South Africa

Oxidation of iron-rich rock is known to generate H2 in oceanic as well as in continental domains. Here we tested the possibility of H2 generation as the result of weathering of banded iron formations (BIF). The BIF constitute more than 60% of global iron ore reserves with low Fe3+/Fetot and total Fe ranging from 20 to 40 wt% and are therefore good candidates for H2 production potential. In the vicinity of BIF-hosted iron mines in Australia, Brazil and South Africa, satellite imaging has revealed the presence of sub-circular depressions that usually are the proxy of H2-emitting features. A morphological comparison of the sub-circular depressions with the ones observed in previous studies point to probable H2 seeping in these areas. In parallel, a petrological study conducted on altered and fresh BIF samples from the Hamersley Province in Western Australia also suggests H2 generation during BIF weathering. Indeed, mineral transitions from ferrous silicate (riebeckite and/or minnesotaite) to ferric iron oxi-hydroxides (goethite) or from ferrous and ferric oxides (magnetite) to exclusively ferric oxides (maghemite, hematite, goethite) were observed on the samples. The oxidation of ferrous iron by aqueous fluids circulating through and leaching the BIF is promising for H2 generation. The BIF weathering profile suggests that the limiting factor is the presence of water, and that this reaction is happening at, or near, surface temperature. This challenges the idea that high temperatures are required to generate H2 as it is the case during the serpentinization. The link between BIF and H2 will have however to be further investigated to better constrain the reactions and their kinetics.

Hydrogen Emanations in Intracratonic Areas: New Guide Lines for Early Exploration Basin Screening

Offshore the emissions of dihydrogen are highlighted by the smokers along the oceanic ridges. Onshore in situ measurements in ophiolitic contexts and in old cratons have also proven the existence of numerous H2 emissive areas. When H2 emanations affect the soils, small depressions and vegetation gaps are observed. These depressions, called fairy circles, have similarities with the pockmark and vent structures recognized for long time in the sea floor when natural gas escapes but also differences. In this paper we present a statistic approach of the density, size, and shape of the fairy circles in various basins. New data from Brazil and Australia are compared to the existing database already gathered in Russia, USA, and again Brazil. The comparison suggests that Australia could be one of the most promising areas for H2 exploration, de facto a couple of wells already found H2, whereas they were drilled to look for hydrocarbons. The sum of areas from where H2 is seeping overpasses 45 km2 in Kangaroo Island as in the Yorke Peninsula. The size of the emitting structures, expressed in average diameter, varies from few meters to kilometers and the footprint expressed in % of the ground within the structures varies from 1 to 17%. However, globally the sets of fairy circles in the various basins are rather similar and one may consider that their characteristics are homogeneous and may help to characterize these H2 emitting zones. Two kinds of size repartitions are observed, one with two maxima (25 m and between 220 m ± 25%) one with a simple Gaussian shape with a single maximum around 175 m ± 20%. Various geomorphological characteristics allow us to differentiate depressions of the ground due to gas emissions from karstic dolines. The more relevant ones are their slope and the ratio diameter vs. depth. At the opposite of the pockmark structures observed on the seafloor for which exclusion zones have been described, the H2 emitting structures may intersect and they often growth by coalescence. These H2 emitting structures are always observed, up to now, above Archean or Neoproterozoic cratons; it suggests that anoxia at the time the sedimentation and iron content play a key role in the H2 sourcing.

A Summary of “Future Advances in Basin Modeling: Suggestions from Current Observations, Analyses and Simulations”

The objective of this volume differs from that of the usual review of current advances [...]

Earth Tides and H2 Venting in the Sao Francisco Basin, Brazil

Hydrogen gas seeping from Proterozoic basins worldwide is a potential non-carbon energy resource, and the vents are consequently receiving research attention. A curious feature of H2 venting in the Sao Francisco Basin in Brazil is that the venting displays a very regular daily cycle. It has been shown that atmospheric pressure tides could explain this cycle, but solid earth tides might be an alternative explanation. We show here that it is unlikely that solid earth tides are a dominant control because they have two equally strong peaks per day whereas the H2 venting has only one.