Drainage and imbibition CO2/brine relative permeability curves at in situ conditions for sandstone formations in western Canada

One of the most important mechanisms for CO2 storage in deep saline aquifers is CO2 trapping at irreducible saturation, which depends on the relative permeability characteristics of CO2/brine systems. CO2 injectivity, pressure build-up and the evolution and long-term fate of the injected CO2 also depend on the same relative permeability characteristics. Predicting the fate of the injected CO2 using numerical models requires adequate relative permeability relationships for CO2/brine systems (both drainage and imbibition cycles), yet very few experimental data exist in the literature. Considering that CCS will be deployed on a large scale in western Canada, three experimental programs of determining the relative permeability characteristics at in-situ conditions of prospective storage aquifers have been successively run between 2003 and 2011. The first two programs focused on testing rocks from various deep carbonate and sandstone aquifers in central Alberta in the vicinity of several very large CO2 sources. The third testing program focused on measuring the relative permeability for CO2/brine systems at various locations in the sandstone Basal Aquifer that overlies the Precambrian basement in western Canada. The results of the first testing program, comprising 14 measurements, have been published in 2008. The results for relative permeability testing on eight additional carbonate rocks have been published in 2010 and combined with the results for five tests from the first measurement program to obtain generalizations for carbonate rocks. Results of new CO2/brine relative permeability measurements on 16 sandstone rocks from the second and third measurement programs are presented for the first time in this paper. These results are combined with results of testing on six sandstone rocks from the first measurement program, for a total of 22 tests, and are generalized similarly to the generalization for carbonate rocks published previously. The test data cover a very wide range of permeability values, from less than 0.1 mD to more than 500 mD. The generalizations in terms of relative permeability and residual saturation are defined based on rock characteristics that are routinely measured in core analyses, such as pore size and absolute permeability. (C) 2013 The Authors. Published by Elsevier Ltd.