Alain Prinzhofer, after a diploma of engineer from the Ecole Nationale Supérieure des Mines de Paris (France), defended a PhD on Structural geology and petrology in the ophiolitic complex of New Caledonia in the Ecole Nationale des Mines de Paris. He defends a Thèse d’Etat” (French State Doctorate) in geochemistry in the IPGP (Institut de Physique du Globe de Paris), devoted to the processes of mantle partial melting in extensive areas. He worked then two years in Caltech (California) on Samarium/Neodymium isotopes in meteorites. He works then 20 years in IPFEN (Institut Français du Pétrole et des Energie Nouvelles), where he focuses mainly on gas geochemistry (hydrocarbon, non-hydrocarbon compounds, stable isotopes and noble gas isotopes). Creating a laboratory of stable isotopes and of noble isotopes, his research deals with various issues concerning gas sources, generation, migration, contamination and alteration. After 3 years in the O&G company HRT (Brazil), he creates the service and research company GEO4U (Brazil). He works today on the geochemistry of natural gas in general, but his main interest is now the exploration of natural hydrogen on the planet, both in ophiolitic environments than in continental cratons. He is the author of more than 50 Rank A scientific papers in journals and book chapters, 8 patents, more than 150 communications in congresses, and wrote a book on natural hydrogen with Eric Deville. He teaches in various French and foreign universities on applied geosciences (mining geology, petroleum systems and Earth Sciences associated with energy).
25 novembre 2024 -
11h15 -
12h30
How the H2 is moving in subsurface: New concepts and software for H2 generation/transport/accumulation -
Noble gas isotopes: efficient tracers for the characterization of natural hydrogen accumulations
Exploration of natural hydrogen in various geological contexts (ophiolites, cratons, superficial macro-seeps and subsurface accumulations discovered through drilling) gives today a decent geochemical database on gas concentrations (hydrogen, nitrogen methane, helium and other noble gases), as well as isotopic ratios (Hydrogen, carbon, nitrogen, noble gas isotopes).Several fundamental questions related to natural hydrogen are still under discussion:- Is a hydrogen system a renewable system at human time scale?- Why nitrogen and helium are always associated with hydrogen in various proportions, whereas their generation is generally not related to the hydrogen generation as understood today?- How to quantify the interest of a hydrogen system, in terms of future production?- While hydrogen fields will be produced, will the gas composition remain constant through time, or could occur a shift of gas composition versus the amount of produced gas?Fossil noble gas isotopes (20Ne, 36Ar, 84Kr for example) are present in the Earth atmosphere, and in aquifers equilibrated with the air concentrations (ASW). They represent very simple geochemical natural tracers in gas phases, as their sources are very well characterized, as well as their physical properties. As they are chemically inert, any observed fractionation needs to be related to physical processes as phase exchanges (in our case, only water and vapor phases), diffusion and adsorption/desorption on solid surfaces. Radiogenic noble gas isotopes as 4He and 40Ar, which amounts are increasing with time, present chronometers associated with the geological fluids.Fossil isotopes, measured in various geological occurrences of natural hydrogen, present a good consistency, and indicate clearly that they suffered large physical fractionations, which cannot be related to any simple mixing process between geological reservoirs. Their behavior is very different than when associated with hydrocarbon accumulations. We demonstrate that they suffered a fractionation linked to their extraction from aquifer water and desorption from solid surfaces into a gas phase (hydrogen blend gas), and that this extraction is occurring in an open system for natural hydrogen systems, whereas it occurs in an almost closed system in petroleum systems.A simple modelling allows to confirm the open dynamics of hydrogen gas in geological formations, where accumulations are related to bottleneck effect rather than to a complete sealing process. It was also possible to compare the efficiency of this steady-state accumulation in various case studies, as well as the efficiency of hydrogen generation for various geological hydrogen systems.
