Origin of gases exhaled by structural accidents in southern Aquitaine

Laurent Truche – Université Grenoble Alpes
Frédéric Donzé – Université Grenoble Alpes 
Eric Gaucher – Total, CSTJF, Pau

Major Results

Hydrogen targeting using soil gas analysis (H2, CO2, CH4, Rn, He) shows a non-random distribution. All high values are located near the North Pyrenean Frontal Thrust (NPFT)
Summary (pitch) of the most important result(s) derived from your thesis/post-doc work.


Natural hydrogen (H2) seepages may represent a new promising source of energy for a low carbon society. Numerous geological evidences of natural H2 seepages and accumulation are now well identified, but our knowledge of hydrogen behavior in the crust is so limited that it is not yet possible to consider exploitation of this resource. To date, there is neither exploration strategy nor any resource assessment, as practical guidelines for hydrogen targeting are missing. Here, we lay the foundation of a new targeting approach dedicated to H2 exploration, using the Pyrenean orogenic belt and its northern foreland basin as a playground. This latter geological setting represents a promising framework to investigate a potential H2 system, as all the conditions for H2 generation, migration/drainage are gathered. Geophysical data indicate the presence of a massive mantle body at shallow crustal level ( < 10 km depth) below the Mauleon Bassin. This mantle body is connected to the surface by two major faults : North Pyrenean Frontal Thrust (NPFT) to the north and North Pyrenean fault (NPF) to the south. >


We perform surface survey of soil gas with 550 measurements lie on a 100×80-km grid corresponding to the North Pyrenean Zone (NPZ). Soil gas are analyzed with a Gas Analyzer (GA 5000) and a portable radon monitoring (AlphaGuard DF2000). It appears the mapping H2 concentration show a circular anomaly around the Mauleon Basin (Fig. 1) and 222Rn, CO2 anomaly is measured above the NPFT. It appears that mapping H2 concentration anomaly in soils and outcropping rock formations at different scales is already extremely instructive when superimposed to geological, seismic, and gravimetric data. Now Noble gas measurements and gas sampeling in order to do isotopic analysis (δ13C-CO2 CH4 and δD-CH4) are also carried out to better constrain their sources of these gases.

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

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

Frédéric-Victor Donzé, Laurent Truche, Parisa Shekari Namin, Nicolas Lefeuvre and Elena F. Bazarkina. Migration of Natural Hydrogen from Deep-Seated Sources in the São Francisco Basin, Brazil. Geosciences 2020, 10(9), 346

keywords: native hydrogen; H2 exploration; gas seeps; H2 venting; radiolysis; serpentinization; draining faults; intra-cratonic basin