Hydraulic properties measurement of tight sandstone for CO2 geological storage

Abstract

Permeability is one of the important rock properties in oil and gas exploration as essential input data of reservoir characterization and production simulation. As production of unconventional resources such as tight gas/oil, shale gas and coal bed methane increases, there is a growing need to measure the permeability of tight formation rocks. Direct measurement by conventional steady-state flow methods, however, is limited due the length of time needed for pressure equilibration. In this study the pressure pulse-decay method is applied to measure low permeability (lower than 9.87E-18m2) rocks. This method is based on the analysis of unsteady-state gas flow. The dissipation rates of dimensionless differential pressure (ΔPD) with time indicates permeability of various core samples. The low permeability measured by using the pressure pulse-decay method, is compared with the permeability recovered from the steady-state method for validation. These low permeability measurements are conducted to six tight sandstones from the Gyeongsang and Janggi basins, South Korea and Tsushima Island, Japan. The apparent permeability measured by the pressure pulse-decay method was approximately twice higher than permeability measured by steady-state method. By comparing the relationship between permeability and mean pressure, this may result from gas slippage effects.