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WATER RESOURCES RESEARCH, VOL. 42, W12418, doi:10.1029/2005WR004806, 2006

Impact of relative permeability hysteresis on geological CO2 storage

R. Juanes

Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA


E. J. Spiteri

Chevron Energy Technology Company, Houston, Texas, USA


F. M. Orr Jr.

Department of Petroleum Engineering, Stanford University, Stanford, California, USA


M. J. Blunt

Department of Earth Science and Engineering, Imperial College London, London, UK


Abstract

Relative permeabilities are the key descriptors in classical formulations of multiphase flow in porous media. Experimental evidence and an analysis of pore-scale physics demonstrate conclusively that relative permeabilities are not single functions of fluid saturations and that they display strong hysteresis effects. In this paper, we evaluate the relevance of relative permeability hysteresis when modeling geological CO2 sequestration processes. Here we concentrate on CO2 injection in saline aquifers. In this setting the CO2 is the nonwetting phase, and capillary trapping of the CO2 is an essential mechanism after the injection phase during the lateral and upward migration of the CO2 plume. We demonstrate the importance of accounting for CO2 trapping in the relative permeability model for predicting the distribution and mobility of CO2 in the formation. We conclude that modeling of relative permeability hysteresis is required to assess accurately the amount of CO2 that is immobilized by capillary trapping and therefore is not available to leak. We also demonstrate how the mechanism of capillary trapping can be exploited (e.g., by controlling the injection rate or alternating water and CO2 injection) to improve the overall effectiveness of the injection project.

Received 13 December 2005; accepted 21 August 2006; published 23 December 2006.

Keywords: carbon sequestration; hysteresis; multiphase flow; porous media; trapping; water-alternating-gas.

Index Terms: 1832 Hydrology: Groundwater transport; 1829 Hydrology: Groundwater hydrology; 1847 Hydrology: Modeling; 1859 Hydrology: Rocks: physical properties.

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Citation: Juanes, R., E. J. Spiteri, F. M. Orr Jr., and M. J. Blunt (2006), Impact of relative permeability hysteresis on geological CO2 storage, Water Resour. Res., 42, W12418, doi:10.1029/2005WR004806.