Abstract
The former Vaux-en-Bugey field, first French methane production from early 20th century, is revisited as a case study to address the present generation and accumulation theories for gases like hydrogen and helium. The volume of the initial gas in place is estimated to be 22 million m3. Based on a composition of 5% of hydrogen and 0.096% of helium, the volumes of these gases in the field were respectively around 1.1 million m3for hydrogen and 24 000 m3for helium. The different hypotheses of hydrogen sources are reviewed: serpentinization, hydro-oxidation of siderite, water radiolysis, bio-fermentation, mechanical generation, degassing from depth trough faults, steel corrosion. For helium generation, the different sources of radioactive minerals and intermediate accumulations are examined. The most probable scenario is the hydrogen production by water radiolysis and helium production by radioactive decay in or near the basement, migrating trough deep faults, stored and concentrating in an aquifer with thermogenic methane, then flushed by methane into the gas field, during Jura thrusting. New measurements with portable gas detector, incomplete but including hydrogen, on a former exploration well with accessible flux of gas, give the opportunity to comment gas saturation evolution more than a century after the 1906 discovery. The decreasing of hydrogen content since the discovery of the field is probably due to Sulphate-Reducing Bacteria activity.
Highlights
Hydrogen is an attracting fuel, because it does not produce CO2 when burning
Most of the hydrogen used in the world comes from natural gas and its interest to de-carbonize is not obvious, except if CO2 released during the process is captured and sequestrated
The objective of this work is to test the different hypothesis of generation and migration of gases, focussed on hydrogen and helium, for the specific case of Vaux-en-Bugey field consistently with the specific geological setting
Summary
Most of the hydrogen used in the world comes from natural gas (by methane reforming) and its interest to de-carbonize is not obvious, except if CO2 released during the process is captured and sequestrated. Since a couple of years, hydrogen started to be produced by water electrolyze using renewable electricity (when not used in the grid). This type of production, named Power to Gas, can contribute to global warming mitigation and could give the opportunity to store energy. Storing hydrogen in existing underground gas storage facilities or dedicated storage facilities is possible for salt cavern storage facilities and currently under discussion for porous reservoirs. Research or pilot projects are launched to understand how hydrogen behaves in the subsurface (Marcogaz, 2016)
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