PhD (M/F) - Characterization of Natural Hydrogen-Producing Systems Using Seismology and Numerical Modeling

Job Description

Thesis Subject

This project aims to understand deformation-controlled hydrogen systems by integrating seismic observations and THMC physical modeling at three complementary sites: Comminges (primary target), Oman, and New Caledonia. The central hypothesis is that seismicity serves as an observable proxy for the coupled processes linking deformation, permeability evolution, fluid circulation, and hydrogen generation. The strategy consists of extracting quantitative seismic observables and testing their consistency with competing physical models.

Comminges (Occitanie) – Primary Application Target
The Comminges prospect is a unique natural laboratory with significant industrial relevance. An extensive dataset has been acquired over the past three years, including reflection seismic data, borehole data, soil gas measurements, and large-scale passive seismic experiments (HOREX® and Full-HOREX®). These deployments, involving more than 2,000 nodal sensors, provide high-resolution imaging of the subsurface over an 80 × 80 km area to a depth of ~20 km. Preliminary results reveal a complex system featuring a high-seismic-velocity body interpreted as a potential hydrogen-generating zone (the “hydrogen kitchen”), associated with fluid-rock interaction processes, serpentinization, and seismicity. However, the mechanisms controlling seismicity and hydrogen migration remain uncertain. The doctoral thesis will analyze diagnostic seismological observables, including: the spatial distribution and migration of seismicity, magnitude-frequency statistics and temporal clustering, source properties (strain drop, duration, moment-duration scaling), and velocity anomalies (Vp, Vp/Vs).
These observations will be quantitatively compared with model predictions to test whether the system is dominated by the geometric interactions of the faults, the rheological properties of the fault zone, or processes driven by fluids and chemical reactions. The ultimate goal is to reduce uncertainty regarding the presence, geometry, and dynamics of hydrogen-generating zones, and to evaluate the predictive value of seismic observations for exploration.

Oman—a controlled analogous system
The Samail ophiolite is a simplified, well-constrained system where mantle rocks outcrop at the surface and interact with meteoric fluids, allowing for the direct observation of active serpentinization and hydrogen generation. A joint active-passive seismic experiment, including controlled water injection into wells, allows monitoring of the system's response to a known disturbance. This offers a unique opportunity to establish causal relationships between variations in fluid pressure, fracture activation, seismicity, and H₂ generation. Oman will serve as a reference system for calibrating the link between seismic observables and fluid-driven processes, and for distinguishing between mechanical and hydraulic controls on seismicity.

New Caledonia—An Intermediate-Type System
New Caledonia presents an intermediate level of complexity, combining active serpentinization, intense deformation, and hybrid hydrological conditions (humid tropical, oceanic). The system is characterized by extensive existing datasets (geochemistry, hydrogeology, seismic, magnetotelluric), supplemented by new data acquired as part of Ifremer's INCOGNITO project. This site allows for the study of deformation-fluid coupling at various scales, from the continental to the offshore domain, and provides key constraints on the permeability structure and hydrogen migration pathways.

Integrated Approach and Modeling Framework
The project is based on a multiscale observation strategy that combines dense nodal seismic networks, distributed acoustic sensing (DAS) via fiber optics, and active seismic data to detect and characterize seismicity across the entire deformation spectrum (earthquakes, tremors, slow-slip events). These observations will be interpreted within a THMC physical modeling framework, in which deformation controls the evolution of permeability, fluid pressure evolves via porous flow, and reactions (serpentinization) modify bulk and mechanical properties. The objective is to determine which combinations of processes can reproduce the observed seismic signatures. By comparing observations and model predictions across the three sites, the project will identify the mechanisms controlling hydrogen generation and migration, quantify the role of strain-induced permeability, and evaluate the diagnostic value of seismic observables. This approach ultimately aims to develop predictive tools for the exploration and monitoring of natural hydrogen, grounded in physically consistent models and validated by multi-site observations.

Your Work Environment

The GET is a member of the Observatoire des Sciences de l'Univers (OSU) “Observatoire Midi-Pyrénées” (OMP) federation, which is overseen by the CNRS, CNES, IRD, Météo-France, and the University of Toulouse. It currently has a staff of 226 people, including 156 permanent employees (52 from the CNRS, 55 from UT/CNAP, 38 from the IRD, and 11 from the CNES) and more than 70 doctoral students and researchers on fixed-term contracts.

The GET is affiliated with the CNRS's “Earth & Universe” (INSU) and “Ecology and Environment ” (INEE) of the CNRS, the “Internal and Surface Dynamics of Continents” (DISCO) department of the IRD, and the “Earth – Oceans – Continental Surfaces – Atmosphere” (TOSCA) domain of the CNES. Since 2011, the GET has also been an affiliated unit and a component of the Carnot Institute ISIFoR (Sustainable Engineering of Georesources).

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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