Parameter Screening Study for Optimizing the Static Properties of Nanoparticle-Stabilized CO2 Foam Based on Orthogonal Experimental Design

Nanoparticle (NP)-stabilized foam technology has found potential applications in CO 2 enhanced oil recovery (EOR) and greenhouse gas geological storage practices and accordingly attracts lots of research interest. To screen the optimal formula for the satisfactory foam performance, orthogonal experimental design (OED) is used in this paper for the complex multifactor multilevel system consisting of five influential factors of NP size, surfactant concentration, NP concentration, temperature, and salinity at four different levels in the range of 7-40 nm, 0-0.15 wt %, 0-0.2 wt %, 25-55 °C, and 0-3 wt %, respectively. Based on the orthogonal principle, only 16 experiments were performed to analyze the effect of various factors on the foam height and foam half-life properties. In addition to showing that the influence of the single factor on foam static properties, OED results reveal that the surfactant concentration and temperature are dominating factors on foamability and stability of the NP-stabilized CO 2 foam, respectively. Finally, NP-stabilized CO 2 foam with satisfactory static characteristics is obtained with the OED recommended composition of a 0.15 wt % surfactant concentration, 0.1 wt % NP concentration, and NP size of 7 nm in 1 wt % saline solution at temperatures of 30 and 50 °C, validating that the OED method could substantially facilitate the laboratory screening and optimization process for a successful NP-stabilized CO 2 foam application.