Dynamic adsorption of switchable amine surfactants on carbonate under reservoir conditions: Implications for foam assisted CO2 storage

Highlights

• ?A more accurate approach for estimating the adsorption of switchable amine surfactants was developed.
• ?The novel approach can reproduce all the essential geochemistry reactions at reservoir conditions during CO2 injection.
• ?The pH, salinity, brine compositions, surface charge, and mineral wettability can be primarily preserved.
• ?Static adsorption tests may overestimate the adsorption level of switchable amine surfactant.
• ?The CO2 and foam transport behavior is primarily influenced by surfactant adsorption and partitioning behavior.

The efficacy of the foam-assisted CO2 sequestration process is primarily determined by the degree of surfactant adsorption in the field. Nevertheless, the dynamic adsorption behavior of the switchable amine surfactants, a predominant type of CO2 soluble surfactants, remains challenging due to their distinct solubility in brine under typical reservoir conditions. The investigation involved conducting dynamic adsorption tests on Indiana limestone rock samples at reservoir conditions (e.g., 65?°C and 150?bar) by co-injecting a suitable fraction of CO2 with the surfactant solution. These circumstances ensured the complete solubilization of CO2. The desired co-injected volume of CO2 can be estimated by the Peng-Robinson equation of state model or visualization experiments, given specified reservoir conditions. The pH of the brine saturated with CO2 and the charge of the mineral surface are strongly influenced by the pressure of CO2. As a result, the adsorption behavior of surfactants on minerals might be affected. This approach allows for preserving various factors such as pH, salinity, brine compositions (including potential determining ions), surface charge, and mineral wettability. It is capable of accurately reproducing all the necessary geochemical reactions between CO2, brine, and minerals under reservoir conditions during CO2 injection. The dynamic adsorption of amine surfactants on limestone is minimal (0.089–0.113?mg/g or 0.0307–0.0389?mg/m2) when high-pressure CO2 is present. However, the static adsorption tests may significantly overestimate the adsorption levels (0.32–0.43?mg/g or 0.0571–0.0597?mg/m2) since the testing conditions typically differ from the actual reservoir conditions. The dynamics of CO2 and foam transport are primarily determined by the interplay of surfactant adsorption and partitioning behavior. This study presents a reliable approach for accurately estimating the adsorption of switchable amine surfactants at aquifer conditions. The approach demonstrates good reproducibility and surpasses the previous static adsorption method in accuracy. This estimation is crucial for evaluating the viability of foam-assisted carbon storage.