Influence of stearic acid and alumina nanofluid on CO wettability of calcite substrates: Implications for CO geological storage in carbonate reservoirs.

Hypothesis: Atmospheric CO emissions trigger global warming and climate change challenges. Thus, geological CO storage appears to be the most viable choice to mitigate CO emissions in the atmosphere. However, the adsorption capacity of reservoir rock in the presence of diverse geological conditions, including organic acids, temperature, and pressure, can cause reduced certainty for CO storage and injection problems. Wettability is critical in measuring the adsorption behavior of rock in various reservoir fluids and conditions.

Experiment: We systematically evaluated the CO-wettability of calcite substrates at geological conditions (323 K and 0.1, 10, and 25 MPa) in the presence of stearic acid (a replicate realistic reservoir organic material contamination). Similarly, to reverse the effects of organics on wettability, we treated calcite substrates with various alumina nanofluid concentrations (0.05, 0.1, 0.25, and 0.75 wt%) and evaluated the CO-wettability of calcite substrates at similar geological conditions.

Findings: Stearic acid profoundly affects the contact angle of calcite substrates where wettability shifts from intermediate to CO-wet conditions, reducing the CO geological storage potential. The treatment of organic acid-aged calcite substrates with alumina nanofluid reversed the wettability to a more hydrophilic state, increasing CO storage certainty. Further, the optimum concentration displaying the optimum potential for changing the wettability in organic acid-aged calcite substrates was 0.25 wt%. The effect of organics and nanofluids should be augmented to improve the feasibility of CO geological projects at the industrial scale for reduced containment security.