Volcanic rocks often have sufficient porosity and permeability to provide suitable reservoirs for fluid storage, carbon sequestration and geothermal and hydrocarbon production. Presently, physical properties of lava domes are mostly discussed in the context of their formation where highly permeable lava domes are more efficient at degassing and thus are less likely to experience explosive eruptions. Petrophysical and geophysical properties of three coeval lava domes within the Taupō Volcanic Zone are presented at atmospheric pressure with further geophysical analysis at reservoir effective pressures with different saturating fluids. Data is compiled from literature, new parameters are measured (porosity, permeability and ultrasonic wave velocities) and the reservoir potential of diverse lava dome lithofacies is investigated.

Lava domes are typically divided into four facies: (i) interior core facies; (ii) basal breccia facies; (iii) carapace facies, and (iv) spine facies. Measurements across 41 core samples show the core facies is of variable porosity (5-25%) and permeability (0.3-1475 mD) and may be utilised as a secondary reservoir; basal breccia is of moderate porosity (14-22%) and permeability (8-1475 mD) and may be utilised as a reservoir or migration pathway; the carapace facies is of high porosity (23-38%) and permeability (21-5703 mD) and would be a primary reservoir target; the spine facies is of low porosity (3-9%) and moderate permeability (4-1650 mD) and could be an exceptional vertical migration pathway.

Seismic waves are commonly used to monitor reservoirs due to their high sensitivity to fluids and can also be used to estimate the elastic stiffness of rocks. Here, a dataset of P and S-wave velocities is presented at atmospheric pressure with experimental results showing that lava dome facies can be partially distinguished based on their velocity-porosity clustering. Furthermore, P-wave velocity changes induced by the addition of water at atmospheric pressure provides a good approximation of pore shape which is corroborated by lithological and petrophysical measurements.

In addition, five samples were experimentally tested for P and S-wave velocities for a range of saturating fluids at in-situ effective pressures (i.e., depths). Based on experimental data, seismic methods are capable of monitoring liquid-CO₂ replacing water in porous and fractured dome facies. Finally, an injection scenario is used to indicate the expected P-wave velocity changes during a complete CO₂-water substitution with a pore pressure increase of 5 MPa.