Capillary pressure and heterogeneity for the CO₂/water system in sandstone rocks at reservoir conditions

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• 作者：Ronny Pini ; ^{pini@stanford.edu} ; Samuel C.M. Krevor ; Sally M. Benson
• 关键词：Capillary pressure ; Heterogeneity ; CO2 sequestration ; Multiphase properties
• 刊名：Advances in Water Resources
• 出版年：2012
• 出版时间：March 2012
• 年：2012
• 卷：38
• 期：Complete
• 页码：48-59
• 全文大小：1785 K

文摘

A novel method is presented to measure drainage capillary pressure curves both at the core and sub-core scale using CO₂ and water at reservoir conditions. The experimental configuration is very similar to the one used in traditional steady-state relative permeability experiments. Capillary pressure measurements are made at the inlet face of the sample by successively increasing the flow rate of the non-wetting phase while measuring the saturation with a medical X-ray Computed Tomography (CT) scanner. The method requires that the wetting phase pressure is uniform across the core and can be measured in the outlet end-cap. A capillary pressure curve is obtained in less than two days, as compared to weeks for existing methods that use porous plates. Drainage capillary pressure curves of CO₂ and water are measured for two sandstones rock cores with different lithology and pore size distribution. Experiments are carried out at 25 and 50 ¡ãC and at 9 MPa pore pressure, while keeping the confining pressure on the core at 12 MPa. There is excellent agreement between the new method and data from mercury intrusion porosimetry; beside providing confidence in the new technique, such comparison allows for an estimate of the wetting and interfacial properties of the CO₂/water system. X-ray CT scanning allows for precise imaging of fluid saturations at a resolution of about (2.5 ¡Á 2.5 ¡Á 1) mm³, thus enabling quantification of sub-core scale capillary pressure curves. These measurements provide independent confirmation that sub-core scale capillary heterogeneity plays an important role in controlling saturation distributions during multiphase flow.