SUMMARY

Carbon capture and storage (CCS) has the potential for reducing CO2 emissions to the atmosphere. This option includes storage strategies such as CO2 injection into deep saline aquifers, depleted oil and gas reservoirs, and unmineable coal seams. This process is largely controlled by the interactions between CO2, the reservoir fluid and reservoir rock. In particular, the wettability of the rock matrix has a strong effect on the distribution of the injected CO2 into geological formations. In this study, the wetting behavior of Bentheimer sandstone slabs and CO2 and/or flue gas is investigated by means of contact-angle measurements. In addition, the interfacial tension between CO2 and/or flue gas and connate water was determined. The experiments were conducted in a pendant-drop cell, adapted to allow captive-bubble contact-angle measurements and performed at a constant temperature of 318 K and pressures varying between 0.2 and 15 MPa, typical in-situ conditions. The experimental contact angle measurements show that the Bentheimer sandstone/water system is (and remains) water-wet even at high pressures with CO2 and/or flue gas injection. The determined data of the contact angle of the water–sandstone system demonstrate a strong dependence on the bubble size and surface roughness with CO2 and flue gas injection