A New Method for the Determination of Foam Capillary Pressures in Porous Media

摘要

This paper reports a new implementation of X-ray computedtomography (CT) to investigate capillary pressures duringfoam flow in porous media. The method is based on thedependence of X-ray attenuation coefficient of gas on itspressure. Gas pressureare obtained from the CT images,together with water saturations, while water pressure ismeasured classically using pressure sensors. The researchshows that the X-ray attenuation coefficient of a corecontaining gas varies linearly with gas pressure, over a widerange of pressures. A similar dependence is found in presenceof irreducible water, which allows determination of theresidual water saturation. More significantly, during transientfoam flow in porous media the gas and capillary pressureshave been determined accurately, using the newly establishedrelation between the attenuation coefficient and pressure. Thecapillary pressure derived from the proposed method, revealsnew aspects of foam behavior, and provides for the first timedirect evidence that the secondary liquid de-saturation is dueto gas expansion, as was suggest in earlier studies.