PETROACOUSTIC CHARACTERIZATION OF FRACTURED LIMESTONES FROM THE VADOSE ZONE OF BEAUCE AQUIFER (O-ZNS, France)

Abdoul Nasser Yacouba (1, 2) , Céline Mallet (1, 2) , Jacques Deparis (3) , Kévin Beck (4) , Gautier Laurent (1) , Philippe Leroy (3) , Mohamed Azaroual (1, 2, 3) , Damien Jougnot (5)

1 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
2 Géosciences pour l'énergie & l'environnement
3 BRGM - Bureau de Recherches Géologiques et Minières
4 LaMé - Laboratoire de Mécanique Gabriel Lamé
5 METIS - Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols

Fluid flow in reservoir rocks are mainly controlled by heterogeneities present at all scales, especially for carbonate reservoirs. Predicting reservoir and acoustic properties becomes tremendously difficult in complex environments like vadose zone. We investigated petroacoustic properties coupled to macroscopic descriptions of limestone samples from the Beauce aquifer vadose zone of the O-ZNS Observatory (Villamblain, France). At first sight, the different samples present highly heterogeneous features defined as macropores (fractures, cracks, dissolution vugs). The petrophysical characterization shows that the reservoir properties are scattered for the samples with important macropores resulting in a poor permeability-porosity relationship. However, the permeability prediction is improved by using pore size as a second controlling factor. Indeed, it is the case for different samples with micritic matrices associated with more or less non-connected micropores. The velocity-porosity correlation and relationship with empirical models shows correlated relations allowing to differentiate samples with respect to their structures. However, we highlighted that the presence of macropores tends to minimize the control of the effective porosity. The influence of density on velocities is very difficult to establish and none of the empirical models allow a satisfying estimation. Finally, applying petroacoustic models highlights a close relationship between the presence of macropores and the dispersion of reservoir and elastic properties.

Mots clés: Petrophysics; Acoustics; Fractured limestones; Vadose zone

Domaines: Géophysique [physics.geo-ph]; Pétrographie; Acoustique [physics.class-ph]

Abdoul Nasser Yacouba, Céline Mallet, Jacques Deparis, Kévin Beck, Gautier Laurent, et al.. PETROACOUSTIC CHARACTERIZATION OF FRACTURED LIMESTONES FROM THE VADOSE ZONE OF BEAUCE AQUIFER (O-ZNS, France). 2024. ⟨hal-04520290⟩