Use of Micro-X-ray CT Analysis for Porosity and Permeability Characterisation of Volcanic Reservoir Rocks

Application of micro-focus X-ray computed tomography (μCT) to a suite of variably altered volcanic rocks allows quantification and 3D visualisation of the pore space down to a μm scale. This provides unprecedented insights into pore morphologies and when combined with traditional petrographic observations, becomes a powerful tool to analyse the interaction of secondary mineralisation with porosity. We determine porosity is controlled by the amount of vesiculation, the abundance of quench fractures and the original glass content. Permeability is often controlled by the degree of vesiculation, whereby samples with vesicle densities greater than 10% show significantly higher permeabilities due to the development of inter-vesicular micro-fractures. Total porosity is enhanced by the hydration of mesostasis and the alteration of phenocryst phases, however μCT visualisation show these micro-pores are not contributors to the volcanic rocks permeability, because they are isolated.