CO₂ Adhesion on Hydrated Mineral Surfaces

Abstract

Hydrated mineral surfaces in the environment are generally hydrophilic but in certain cases can strongly adhere CO2, which is largely nonpolar. This adhesion can significantly alter the wettability characteristics of the mineral surface and consequently influence capillary/residual trapping and other multiphase flow processes in porous media. Here, the conditions influencing adhesion between CO2 and homogeneous mineral surfaces were studied using static pendant contact angle measurements and captive advancing/receding tests. The prevalence of adhesion was sensitive to both surface roughness and aqueous chemistry. Adhesion was most widely observed on phlogopite mica, silica, and calcite surfaces with roughness on the order of ~10 nm. The incidence of adhesion increased with ionic strength and CO2 partial pressure. Adhesion was very rarely observed on surfaces equilibrated with brines containing strong acid or base. In advancing/receding contact angle measurements, adhesion could increase the contact angle by a factor of 3. These results support an emerging understanding of adhesion of, nonpolar nonaqueous phase fluids on mineral surfaces influenced by the properties of the electrical double layer in the aqueous phase film and surface functional groups between the mineral and CO2.

Receding and advancing (CO 2 + brine + quartz) contact angles as a function of pressure, temperature, surface roughness, salt type and salinity

“…A higher surface roughness resulted in lower advancing and receding contact angles, consistent with literature data [40]. Values of h a and h r increased as pressure increased, which is consistent with most literature data [10,12,15,[25][26][27][28][29][30][31].…”

“…This effect thus needs to be analysed further. Increasing salinity also significantly increased h, consistent with literature data [26,[28][29]31,35,[38][39][40], while different salts resulted in different changes. We observed the ranking Mg +2 > Ca +2 > Na + in terms of de-wetting potential, and we explain this effect by cation shielding of the electrical surface charge of quartz [43].…”

“…The h a decreased by 6.5°and h r by 2°when surface roughness was increased from (56 to 1300) nm at T = 296 K and 10 MPa, figure 8, consistent with literature data [40]. This effect was even more pronounced at higher temperature (323 K): h a decreased by $14°and h r by $14°.…”

“…In summary, saline brine resulted in higher contact angles when compared to DI-water, consistent with literature data [14,26,29,31,35,[38][39][40]. The increase in h changed with salt type and followed the ranking MgCl 2 > CaCl 2 > NaCl.…”

Interfacial tension and contact angle in CO2‐water/nanofluid‐quartz system

“…In addition to the de‐wetting phenomenon, the pinning effect is another phenomenon found in the CO 2 ‐water‐mineral system. The pinning effect has always been observed during the diffusion process of droplets . The triple contact line of CO 2 ‐water‐mineral is fixed during the diffusion process.…”