Natural hydrogen generation in granitic geothermal reservoirs of the Upper Rhine Graben, France

MURRAY JESICA; WALLENTIN ANNA; FRITZ BERTRAND; LEMARCHAND DAMIEN; LUCAS YANN; SCHMITTBUHL JEAN

Perth

Simposio; Natural Hydrogen: a sustainable geo-resource for Energy for Australia?; 2023

CSIRO Australia

Non-ultramafic basements in deep continentalhydro-thermal systems are potential context for natural H2 generationthrough the oxidation of Fe2+ minerals in granitic rocks [1,2].This process could represent a process of global magnitude because granites aremajor components of the continental crust. In the hydro-thermal context of theUpper Rhine Graben, France, geothermal brines of up to 200 °C circulate throughgranitic reservoirs at > 2000 m depth.  A high heat flux related toa large temperature gradient up to 110 °C/km in the first kilometre of depth favored the exploitation of severalgeothermal sites producing electricity and heat.  Moreover, several studies at the Soultz-sous-Forêts geothermal site indicate the presence of H2 at 0.25–46.3vol% in the gas phase of hydrothermal fluids [3]. However, the origin of H2 is poorly understood, with some interpretationsrelating its origin to reactions between the metal tubing material and thebrine. To betterunderstand the H2 generation process in this granitic geothermalreservoir, geochemical modeling and water-rock interaction experiments arebeing developed. For that, special attention is paid to hydrothermal alterationof Fe2+-rich minerals in the granite such as biotite, amphibole, chlorite,and magnetite. This research will improve the understanding of abiotic H2generation in deep granitic environments, which had received less attention incomparison to the serpentinization of ultramafic rocks. In the current contextof Energy Transition, the generation of H2 in geothermal sites couldbe seen as an additional decarbonized source of energy together with theproduction of electricity, heat, and critical elements. [1] Murray,et al., (2020), Applied Geochemistry 119, 104631.[2] Truche, et al., (2021),Geochimica et Cosmochimica Acta 308, 42–59. [3] Sanjuan, et al., (2010), Comptes Rendus Geoscience 342, 546–559 .@font-face{font-family:"Cambria Math";panose-1:2 4 5 3 5 4 6 3 2 4;mso-font-charset:0;mso-generic-font-family:roman;mso-font-pitch:variable;mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face{font-family:Calibri;panose-1:2 15 5 2 2 2 4 3 2 4;mso-font-charset:0;mso-generic-font-family:swiss;mso-font-pitch:variable;mso-font-signature:-536859905 -1073732485 9 0 511 0;}@font-face{font-family:CharisSIL;panose-1:2 11 6 4 2 2 2 2 2 4;mso-font-alt:Cambria;mso-font-charset:0;mso-generic-font-family:roman;mso-font-pitch:auto;mso-font-signature:0 0 0 0 0 0;}p.MsoNormal, li.MsoNormal, div.MsoNormal{mso-style-unhide:no;mso-style-qformat:yes;mso-style-parent:"";margin-top:0cm;margin-right:0cm;margin-bottom:8.0pt;margin-left:0cm;line-height:107%;mso-pagination:widow-orphan;font-size:11.0pt;font-family:"Calibri",sans-serif;mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:EN-US;}p{mso-style-noshow:yes;mso-style-priority:99;mso-margin-top-alt:auto;margin-right:0cm;mso-margin-bottom-alt:auto;margin-left:0cm;mso-pagination:widow-orphan;font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:"Times New Roman";mso-ansi-language:ES-AR;mso-fareast-language:ES-AR;}.MsoChpDefault{mso-style-type:export-only;mso-default-props:yes;font-size:11.0pt;mso-ansi-font-size:11.0pt;mso-bidi-font-size:11.0pt;mso-ascii-font-family:Calibri;mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-font-family:Calibri;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;mso-font-kerning:0pt;mso-ligatures:none;mso-ansi-language:EN-US;mso-fareast-language:EN-US;}.MsoPapDefault{mso-style-type:export-only;margin-bottom:8.0pt;line-height:107%;}div.WordSection1{page:WordSection1;}