Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
608135 | Journal of Colloid and Interface Science | 2012 | 10 Pages |
In the context of carbon geo-sequestration projects, brine–CO2 interfacial tension γ and brine–CO2–rock surface water contact angles θ directly impact structural and residual trapping capacities. While γ is fairly well understood there is still large uncertainty associated with θ. We present here an investigation of γ and θ using a molecular approach based on molecular dynamics computer simulations. We consider a system consisting of CO2/water/NaCl and an α-quartz surface, covering a brine salinity range between 0 and 4 molal. The simulation models accurately reproduce the dependence of γ on pressure below the CO2 saturation pressure at 300 K, and over predict γ by ∼20% at higher pressures. In addition, in agreement with experimental observations, the simulations predict that γ increases slightly with temperature or salinity. We also demonstrate that for non-hydroxylated quartz surfaces, θ strongly increases with pressure at subcritical and supercritical conditions. An increase in temperature significantly reduces the contact angle, especially at low-intermediate pressures (1–10 MPa), this effect is mitigated at higher pressures, 20 MPa. We also found that θ only weakly depends on salinity for the systems investigated in this work.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (181 K)Download as PowerPoint slideHighlights► Strong water contact angle increase with pressure increase. ► Strong water contact angle decrease with increasing temperature. ► Minor influence of salinity on the water contact angle. ► Brine–CO2 interfacial tension γ computed with high precision with molecular dynamics for subcritical CO2 pressures.