An experimental study of foams stabilized by anionic and non-ionic surfactants for geological carbon storage in saline aquifers.

Abstract

CCS (Carbon Capture and Storage) is regarded as an important contributor in mitigating CO2 emissions and combating climate change. With increased focus on CCS as an option to reduce CO2 emissions, new CCS projects include saline aquifers as storage sites. However, when injecting pure CO2 into reservoirs, several CO2 mobility challenges such as gravity segregation and viscous fingering result in poor sweep efficiency and limited CO2 storage potentials. These challenges can be overcome by foaming the injected CO2 for increased sweep efficiency and maximize CO2 storage capacity.

This thesis completed a multiscale screening of foam formulations stabilized by anionic and non-ionic surfactants in the presence of synthetic brine compositions. Foam properties such as foam stability, foamability, half-life, apparent viscosity, optimal foam quality and adsorption in bulk and flowing foam were investigated.

Initially, 50 different surfactant solutions were compared in the bulk experiment through performance indicators such as foam stability and foamability. The most favourable solutions were further analysed in the flowing foam and adsorption experiments through foam quality scans and static adsorption tests. Foams stabilized by AOS surfactants had greater foamability compared to foams stabilized by Surfonic surfactant for the chosen surfactant solutions. Divalent ions in brine such as SO4(−2) and Ca2+ appear to positively influence the foamability and foam stability of foams stabilized by AOS surfactant, and maybe to a lesser degree foams stabilized by Sulfonic surfactant. In the bulk experiment, the foam stability of the chosen AOS surfactant solutions was consistently high, whereas the foam stability of the chosen Surfonic surfactant solutions was consistently low. Changes in ionic strength were not found to have any influence on the foamability and foam stability of either surfactant.

When comparing the results of the bulk foam experiment, where AOS had substantially better foamability and foam stability, with the flowing foam experiment, where AOS and Surfonic had comparable apparent viscosity and where Surfonic had a higher MRF, the experiments points towards the conclusion that there is are no direct correlations between dynamic foam properties in bulk foam experiments, and dynamic foam properties in flowing foam experiments.