Experimental and numerical analysis on the specific storage of low permeable sandstone for supercritical CO₂

Experimental tests and numerical analysis were undertaken to investigate the specific storage of sedimentary rocks for supercritical CO₂. New laboratory system of constant flow pump permeability test was developed in order to measure permeability and specific storage of sedimentary rock in similar physical condition of deep aquifer where CO₂ tends to be in supercritical phase. To analyze experimental results, numerical analysis was established by extending the theoretical model of constant flow permeability to deal with two phase flow drainage displacement. For the examination of its applicability, experimental test was undertaken in which Ainoura sandstone used as core sample, injected with supercritical CO₂ under laboratory condition of 35°C constant reservoir temperature, 10 MPa initial hydraulic pressure, and 20 MPa constant overburden pressure The experimental results show that, average specific storage of Ainoura sandstone is about 3.74×10^-4 1/Pa at a maximum CO₂ saturation of 0.55, and volumetric strain increases about 0.7%. The accuracy of specific storage measured was validated with ratio of the specific storage of the sandstone to the storage capacity of the pump used in the permeability test. This finding suggested that newly developed constant flow pump technique with its numerical analysis can be used to effectively obtain specific storage of sedimentary rock for CO₂ in supercritical phase.