Measurement of specific storage of rock for supercritical carbon dioxide using constant flow pump and constant head permeability techniques

Advanced laboratory system of rock permeability test associated with constant flow pump, and constant head permeability techniques were developed to measure permeability and specific storage of rock for supercritical CO₂. The laboratory system was designed to be capable in reproducing similar physical condition of deep aquifer within high pressure and high temperature where CO₂ tends to be in supercritical state. To analyze the result of permeability tests, mathematical models of constant flow pump and constant head permeability techniques were modified to deal with two-phase flow drainage displacement of CO₂-water in rock. For the examination of its applicability, experimental tests and numerical analysis were undertaken. The accuracy of the obtained specific storage was validated by employing a ratio of the specific storage of the rock specimen to the storage capacity of the pump used in the permeability test. It was found that the specific storage of low permeability sandstone for storing supercritical CO₂ is 1.63 × 10⁻⁴ 1/Pa, while large permeability sandstone has the specific storage for supercritical CO₂ at 1.12 × 10⁻⁷ 1/Pa. This finding suggested that advanced experimental system of constant flow pump and constant head permeability technique can be used as repeatable, accurate and standardized laboratory test in measuring specific storage of sedimentary rock for CO₂ in supercritical state.