JC. Ferran1, T. Kremer1, C. Laine2, L. Peignard2, J.M. Ars1, C. Voisin1.
1 Geolinks Services, 2 45-8Energy.
Exploration strategies for uncovering reserves of naturally occurring green gases - such as helium and hydrogen - necessitate advanced geophysical techniques to identify and map potential subsurface reservoirs or pathways. Enhancing our comprehension of the subsurface dynamics of these sought-after resources, still largely unexplored, is crucial. This study focuses on the Fonts-Bouillants research permit held by 45-8 Energy in France, aiming to capture and exploit gases rich in helium and carbon dioxide naturally escaping from the subsoil through thermo-mineral sources.
Geophysical and geological (GG) exploration on the permit site significantly augmented subsurface knowledge, leading to an updated geological model. This first exploration phase implemented various technics and approach, including gravimetry, magnetic data reprocessing, electrical resistivity (ERT), controlled source electromagnetic (CSEM), audio-magnetic-telluric (AMT) profiles, 2D and 3D seismic reflection, geochemical analyses, drilling, and well testing.
This paper introduces how passive seismic and more specifically ambient seismic noise interferometry approach can help expand the subsurface knowledge at an exploration site. In addition to seismic velocity characterization, we introduce the Coherence analysis of Cross-correlated Waveforms (CCW) method, an innovative ANSI-based approach which was recently applied to the monitoring of geological gas storage sites (Kremer et al., 2022a, 2022band shows an ability in detecting and tracking subsurface gas movements. Our investigation explores the method's applicability to tracking naturally occurring green gases and investigate the complementary information it can offer within the overall exploration strategy. The paper sequentially focuses on the method's theoretical basis, the implementation constraints of field surveys, the data processing strategy, and finally the CCW results obtained at the Fonts-Bouillants permit area.