Nanotechnology for improved CO2 utilization in CCS: Laboratory study of CO2-foam flow and silica nanoparticle retention in porous media

作者：Rognmo A U; Horjen H; Ferno M A^*

来源：International Journal of Greenhouse Gas Control, 2017, 64: 113-118.

DOI：10.1016/j.ijggc.2017.07.010

• CCS
• CO2-foam
• Nanoparticles Flow in porous media
• Foam hysteresis
• Nanoparticle retention

Underground CO2 storage may reduce anthropogenic CO2 emissions, but suffer from detrimental flow instabilities mainly from development of viscous fingers and density segregation that arise at larger scales. Suggested approaches to mitigate reduction in CO2 utilization include mobility control, conformance modifications and CO2 thickeners, where CO2 foams have been shown as one of the most promising techniques. We present laboratory results that study foam generation and flow by adding hydrophilic silica nanoparticles during co-injection with liquid CO2 in sandstone core plugs to reduce CO2 mobility. Nanoparticle retention characteristics in the porous media is essential to CO2-foam flow strategies: high degree of retention may, in addition to reducing foamability, be detrimental to fluid injectivity if particle accumulation reduce the formation fluid flow capacity near the injection well. Retention was 401 pg/g, in the lower range of reported literature values for aqueous surfactants, suggesting that nanoparticles to a large degree remain at the CO2-brine interface to stabilize foam when flowing through the porous medium. Elution, recovery of nanoparticles from the pore space by re mobilization, was 79 vg/g. Hence, 20% of retained nanoparticles were re-mobilized, and will contribute positively in a field application to increase foam stability further from the injection well. An apparent foam viscosity hysteresis related to the average gas saturation was observed when drainage-like (increasing gas fractions) and imbibition-like (decreasing gas fractions) injection strategies were compared. Nanoparticle-stabilized foam was also compared with surfactant-stabilized foam and the following main differences were observed: 1) maximum surfactant-stabilized foam apparent viscosities occurred at f(g) = 0.9, compared with nanoparticle-stabilized foam with f(g) = 0.7 (drainage-like) and f(g) = 0.35 (imbibition-like); 2) without the presence of oil surfactant-stabilized foam have a higher (three orders of magnitude) apparent viscosity compared with nanoparticle-stabilized foam; 3) shear-thinning behavior was observed with surfactant-stabilized foam, whereas close to Newtonian behavior was observed with nanoparticle-stabilized foam; 4) no hysteresis was observed with surfactant-stabilized foams, whereas a clear hysteresis was observed with nanoparticle-stabilized foam.

• 出版日期2017-9