Drainage and imbibition relative permeability relationships for supercritical CO2/brine and H2S/brine systems in intergranular sandstone, carbonate, shale, and anhydrite rocks

Disposal of acid gas, composed of carbon dioxide (CO2) and hydrogen sulfide (H,S), in deep underground formations is a means for reducing atmospheric emissions of toxic and greenhouse gases produced from sour-gas reservoirs that has been practiced for 18 years in North America and is currently being considered in other regions, such as the Middle East and central Asia. Acid-gas-injection operations constitute a commercial-scale analog to CO2 injection in geological media as a climate-change mitigation measure. Deep saline aquifers provide a very large capacity for the sequestration of acid and greenhouse gases, being found in all sedimentary basins around the world. Proper understanding of the relative permeability-displacement character of such systems is essential in ascertaining gas injectivity and migration, and in assessing the suitability, containment, and safety of prospective injection sites. Pure CO2 and H2S represent the compositional end members of acid and greenhouse gases, hence the interest in measuring their displacement properties. This paper presents the detailed experimental equipment and protocols along with the results of a series of relative permeability measurements conducted at full reservoir conditions using supercritical pure CO2 and H2S on samples of intercrystalline sandstone, carbonate, shale, and anhydrite rocks from the Wabamun and Zama areas in Alberta, Canada, where large CO2 sources and several acid-gas-injection operations exist. Results of the relative permeability measurements are presented for each fluid and rock type. The results provide a valuable data set for the evaluation and simulation of acid-gas disposal and CO2-sequestration projects.