Poroelastic approach for hydrogen saturation assessment in flow-through experiments

Accurate quantification of fluid saturation is essential for characterising hydrogen distribution during its underground storage. The unique properties of hydrogen – high compressibility, low molecular weight, and diffusivity – limit the direct transfer of experience from carbon dioxide or natural gas storage, motivating tailored laboratory investigations. This study applies a poroelastic framework that infers fluid saturation from the undrained hydro-mechanical response through the calculation of the Skempton’s B coefficient. This approach is grounded in direct measurements of the isothermal effective bulk modulus of water–hydrogen mixtures under different fluid pressures (9–15 MPa) and water:hydrogen ratios (0·9:0·1–0·1:0·9). Comparison with mixing laws shows that Reuss bound accurately captures the reduction in the effective fluid bulk modulus with increasing hydrogen fraction, whereas Voigt and Brie bounds produce significant deviations, particularly for water saturations below 0·8. Closed-form relations between the Skempton’s B coefficient and fluid saturation are evaluated for consistency with relative permeability data available for Berea sandstone, confirming that Reuss-based estimation agrees with the results obtained by way of the scanning methods. This research introduces a practical alternative where imaging techniques are limited by resolution and signal constraints, offering direct insights into hydrogen occupancy in pore space under in situ multiphase flow conditions.