(42b) Contact Angles in scCO2-Brine-Sandstone Systems Using Sessile Drop and Micro-CT Imaging

Saline reservoir sandstones are the primary storage option for Geologic Carbon Storage. Sandstone pore networks provide ample volume to store carbon dioxide in an environment where it is in a supercritical state. Numerous studies have been conducted to quantify the wettability of similar systems via contact angle measurements. It has been reported that factors other than interfacial tension, such as surface roughness, pore geometry, etc., influence scCO₂ residual trapping in a multiphase system. Sessile drop is one technique used to image single droplets and measure contact angles on either side of the droplet. However, this method does not consider additional forces acting on the interface experienced during geologic storage. More recent laboratory studies have focused on flow-through experiments completed to mimic the in-situ injection and reservoir storage process. Once at residual conditions, the sandstone cores are imaged using micro-computed tomography (micro-CT) scanners and the image stacks are used to measure a range of contact angles.

In this work, six sandstones (Bandera Brown, Berea, Bentheimer, Mt. Simon, Navajo, and Nugget) were used to analyze how contact angles measured using the sessile drop images compare to the contact angle measured using image stacks of the same sandstone cores subject to in-situ flow-through conditions. Preliminary results show sessile drop results in shorter contact angle ranges than those found in micro-CT images and some sandstones result in slightly lower average contact angles than others using both techniques. This suggests different formations result in slightly different contact angle distributions. Sandstone networks contain complex geometries, tortuous flow paths, and mineral topology variation throughout. Using micro-CT images, the impacts of pore connectivity and pore geometry are being analyzed on each core to further the understanding each of these characteristic’s roles in the geologic storage process. Additional sessile drop samples are being prepared with varying surface texture degrees to expand the understanding of the impacts of surface roughness on each of the six sandstone cores. Both geometry and surface roughness analyses will be analyzed together for each sandstone to quantify differences in the final contact angle when each of these parameters are considered.