Natural Hydrogen (Nat-H2)
Lead Research Organisation:
University of Southampton
Abstract
A decarbonised mid-twenty first century society will require fuels for heavy industry including steel and cement, shipping, off-grid transport and energy storage. Hydrogen is a clean future fuel because its only combustion product is water. The most proposed hydrogen production approach is “Green Hydrogen”, which is produced by renewably powered electrolysis of fresh water, but has considerable resource, energy and CO2 demands. “Blue Hydrogen” from natural gas reformation combined with carbon capture and storage is expensive and energy intensive with marginal carbon benefits. Consequently, there is growing global enthusiasm about geological hydrogen resources which may be cost and energy efficient to exploit, where natural hydrogen is formed from water by hydrolysis following oxidation of iron in minerals. Natural hydrogen seeps such as those in Mali, Albania and Turkey have been known for decades and are commonly hosted by altered ultramafic rocks that were once part of Earth’s mantle but are now exposed to groundwaters. Mantle rocks are rich in ferrous iron (Fe2+), reactive with water, and consequently good potential reactants to produce natural hydrogen. Some waters that spring from mantle rocks are highly alkaline (pH~11–13) and strongly reducing due to dissolved hydrogen. However, debate remains about whether these hydrogen seeps are sourced from slowly accumulated geological hydrogen reservoirs or whether hydrogen is continuously produced by on-going low temperature reactions (<100°C).
Until recently, hydrogen production was generally accepted to be a relatively high temperature (~250°C) iron oxidation reaction, which favours the trapping of ancient hydrogen interpretation. However, new chemical and isotopic mapping approaches developed at Southampton now allow us to identify the different episodes of fluid-rock reactions that occurred in different conditions, of which some have the potential to form natural hydrogen. This allows us to test the proposition that low temperature reactions between specific minerals and deep groundwaters may be continuously producing hydrogen through iron oxidation.
This project builds on Southampton-led Oman Drilling Project (OmanDP) research on the Samail ophiolite, Earth’s largest on-land section of ocean crust and upper mantle, to investigate whether low temperature oxidation of altered mantle rocks actively produces natural hydrogen. Our project is timely because our partners 44.01, the EarthShot Prize winning Omani-UK start-up, have recently drilled deep (>1000m) wells into tight, groundwater-free mantle rocks of the Samail ophiolite complementing the shallower (<400m) OmanDP wells. Crucially, drilling has recovered rocks from all depths in the wells. Hydrological pumping tests in the deepest parts of these wells have revealed hitherto unseen phenomena: 1) fresh waters pumped into the deep rocks became salty (~seawater) indicating rapid reaction with wall rocks and the dissolution of minerals, and 2) the waters returned bubbled with hydrogen gas. However, the question remains: Is the hydrogen observed old and released from grain boundaries or inclusions by pumping, or has H2 been produced in situ through the oxidation of the wall rocks at low temperatures?
Our proposal brings together this unique suite of fluid and rock samples, to which we have priority access, with state-of-the-art geochemical mapping and micro-analytical tools complemented by thermodynamic modelling to evaluate the low temperature hydrogen generation potential of Omani mantle rocks. These analytical techniques will illuminate the progressive sequences of fluid-rock reactions, involving iron oxidation and potentially, hydrogen generation. We will establish a standard methodology to objectively evaluate the hydrogen generation potential of ferrous-iron-bearing rocks worldwide.
Until recently, hydrogen production was generally accepted to be a relatively high temperature (~250°C) iron oxidation reaction, which favours the trapping of ancient hydrogen interpretation. However, new chemical and isotopic mapping approaches developed at Southampton now allow us to identify the different episodes of fluid-rock reactions that occurred in different conditions, of which some have the potential to form natural hydrogen. This allows us to test the proposition that low temperature reactions between specific minerals and deep groundwaters may be continuously producing hydrogen through iron oxidation.
This project builds on Southampton-led Oman Drilling Project (OmanDP) research on the Samail ophiolite, Earth’s largest on-land section of ocean crust and upper mantle, to investigate whether low temperature oxidation of altered mantle rocks actively produces natural hydrogen. Our project is timely because our partners 44.01, the EarthShot Prize winning Omani-UK start-up, have recently drilled deep (>1000m) wells into tight, groundwater-free mantle rocks of the Samail ophiolite complementing the shallower (<400m) OmanDP wells. Crucially, drilling has recovered rocks from all depths in the wells. Hydrological pumping tests in the deepest parts of these wells have revealed hitherto unseen phenomena: 1) fresh waters pumped into the deep rocks became salty (~seawater) indicating rapid reaction with wall rocks and the dissolution of minerals, and 2) the waters returned bubbled with hydrogen gas. However, the question remains: Is the hydrogen observed old and released from grain boundaries or inclusions by pumping, or has H2 been produced in situ through the oxidation of the wall rocks at low temperatures?
Our proposal brings together this unique suite of fluid and rock samples, to which we have priority access, with state-of-the-art geochemical mapping and micro-analytical tools complemented by thermodynamic modelling to evaluate the low temperature hydrogen generation potential of Omani mantle rocks. These analytical techniques will illuminate the progressive sequences of fluid-rock reactions, involving iron oxidation and potentially, hydrogen generation. We will establish a standard methodology to objectively evaluate the hydrogen generation potential of ferrous-iron-bearing rocks worldwide.