Capillary pressures and gas relative permeabilities of low-permeability sandstone

Use of a high-speed centrifuge for capillary pressure measurements on low-permeability sandstones has been investigated. Curvatures for air/brine and air/decane displacements are compared. Capillary pressures of up to about 800 psi (5516 kPa) for gas displacing brine were extended over an order of magnitude by measurement of isotherms for desorption of water. Capillary pressures measured by high-speed centrifuge merged satisfactorily with results derived from the desorption isotherms. No distinct irreducible water saturation was observed. Permeabilities to gas at various levels of water saturation were also measured and found to be generally consistent with previous relative-permeability measurements.