CO2 wettability of seal and reservoir rocks and the implications for carbon geo-sequestration

We review the literature data published on the topic of CO2 wettability of storage and seal rocks. We first introduce the concept of wettability and explain why it is important in the context of carbon geo-sequestration (CGS) projects, and review how it is measured. This is done to raise awareness of this parameter in the CGS community, which, as we show later on in this text, may have a dramatic impact on structural and residual trapping of CO2. These two trapping mechanisms would be severely and negatively affected in case of CO2-wet storage and/or seal rock. Overall, at the current state of the art, a substantial amount of work has been completed, and we find that: 1. Sandstone and limestone, plus pure minerals such as quartz, calcite, feldspar, and mica are strongly water wet in a CO2-water system. 2. Oil-wet limestone, oil-wet quartz, or coal is intermediate wet or CO2 wet in a CO2-water system. 3. The contact angle alone is insufficient for predicting capillary pressures in reservoir or seal rocks. 4. The current contact angle data have a large uncertainty. 5. Solid theoretical understanding on a molecular level of rock-CO2-brine interactions is currently limited. 6. In an ideal scenario, all seal and storage rocks in CGS formations are tested for their CO2 wettability. 7. Achieving representative subsurface conditions (especially in terms of the rock surface) in the laboratory is of key importance but also very challenging

Grenzflächenphänomene von Flüssigkeiten in Kontakt mit verdichteten CO2

Die Grenzflächenspannung eines hängenden Tropfens und seine Benetzbarkeit in komprimiertem CO₂ werden gemessen. Beide werden in der Youngschen Gleichung korreliert, um die Grenzflächenspannung eines Feststoffes zu bestimmen. Die Benetzbarkeit eines schmalen Flüssigkeitsfilms wird gemessen und ihre Fluiddynamik wird mit Hilfe des Nusselt-, des Tau- und des Wall-Models bestimmt. Die Geschwindigkeitsverteilung im Film sowie in der Grenzfläche und die Schubspannung an der Filmoberfläche werden berechnet.The pendant drop liquid-vapour interfacial tension and its wettability in dense CO₂ are measured. Both are correlated in the Young-Equation in order to estimate the solid-vapour interfacial tension. The wetting angle of water rivulet is estimated and its fluid dynamics are computed according to the Nusselt, the tau and the wall model. The velocity profile in the film phase and the interface, and the shear stress at the film surface are calculated