Influence of Humic acids on CO₂-quartz wettability: Implications for CO₂ storage

Carbon Geo Sequestration (CGS) is considered an effective way to reduce anthropogenic greenhouse gas emission into the atmosphere. The storage of captured CO2 is mainly geological. Several researchers confirmed Humic Acid (HA) concentration in the deep aquifer at high temperature and high-pressure conditions, which may affect the rock wettability and reduce storage capacities and containment security. One key parameter which affects the wettability of formation in the presence of humic acid is pH. However, there is a lack of information on the relationship of pH, humic acid and wettability of CO2 in storage formation. We measured the effect of pH on the CO2 wettability of storage formation in the presence of humic acid. Advancing and receding contact angles were measured at HPHT conditions (pressure of 12 MPa and temperature of 323 K), using the pendant drop tilted-plate method for various pH (2 to 12) at the humic acid concentration (25 mg/L) and brine salinities (0 and 0.2 M NaCl). We concluded that decreasing pH significantly impacts rock wettability; and shifts water-wet to CO2-wet, thus reducing structural and residual trapping capacities. Therefore, presence of organic acids in reservoir geochemical conditions should be considered to derisk the development of CGS projects.