Hydromechanical and geochemical behavior of a serpentinized harzburgite

Many hydrogeological processes are influenced by fluid infiltration into low-porosity serpentinites and the corresponding coupled hydromechanical-geochemical response. The interpretation of these coupled processes requires detailed measurement of poromechanical parameters and careful water sampling and analysis. We measured the poroelastic properties that control the hydromechanical response - drained bulk modulus K, unjacketed bulk modulus $K_s\text{'}$, and Biot coefficient α - for a serpentinized harzburgite from the Semail ophiolite, Oman. For the Terzaghi effective mean stress of 2.0 < $P\text{'}$ = P$-p$ < 7.0 MPa, the poroelastic coefficients K and α exhibit effective mean stress dependency; the ranges are 17.0 < K < 25.6 GPa and 0.74 > α > 0.60. The unjacketed bulk modulus $K_s\prime$ = 64.4 GPa is measured at $P\text{'}$ = 0 MPa. These parameters are used to interpret the diffusion during pulse decay tests, showing that permeability varies with effective mean stress: 2 × 10⁻²² > k > 5 × 10⁻²² m². Water sampling and analysis of fluid composition provided data on the geochemical processes. The geochemical analyses suggest that no new carbonate and serpentine minerals formed after some 47 weeks of reaction.