Water chemistry role in the stability of CO2 foam for carbon sequestration in water aquifers

Injection of CO2 foam into saline aquifers is a practical method to store CO2; however, generating stable CO2 foam at high temperatures and salinities remains a challenging task. Therefore, this research fully explains the effect of formation water components (NaCl, CaCl2, MgCl2, Na2SO4, and NaHCO3) on the stability of generated foam under harsh conditions. In this regard, a high-temperature and high-pressure (HPHT) foam analyzer was used to investigate the foamability and stability of CO2 foam at 100 degrees C and 1000 psi. The liquid phase contained 0.5 wt% of Armovis surfactant dissolved into 0.1, 0.5, and 1M concentrations of formation water ions. Moreover, the dynamic surface tension of the selected surfactant solutions was investigated using an optical tensiometer. For the first time, this paper investigates the behavior of foam during the foaming process. During the injection of CO2, the average bubble count for the low salt concentration increased sharply and then dropped until it plateaued. However, the average bubble count for the higher salt concentration gradually increased until the foaming process stopped. These phenomena occurred because of the kinetic adsorption rate of the surfactant micelles at the interface. Additionally, we studied the effect of salt concentrations on bubble count half-life, bubble coarsening, and foam volume decay during the static condition. We observed that the increase in salt concentration resulted in more stable foam due to the reduction of CO2 solubility in water. The foam half-life for 0.1 M of NaCl was 190 min, while it was more than 250 min for 1M of NaCl. A similar trend was observed for CaCl2 and MgCl2. The results of the HPHT foam analyzer concluded that the higher concentration of salt ions presented a more stable foam. Also, the use of Armovis surfactant is promising for the stabilization of CO2 foam at high temperatures and salinities.

Automated summary

This research investigates the effect of formation water components on the stability of CO2 foam under harsh conditions. The results show that higher salt concentrations lead to more stable foam, and the kinetic adsorption rate of surfactant micelles is the main factor influencing foam behavior.