Stabilization of CO2 Foam with Silica-Based Nanoparticles Summary

To improve CO2 EOR methods, CO2 foams stabilized by surfactants have been developed to increase fluid viscosity and enhance sweep efficiency. However, at high temperatures, surfactants tend to degrade, which reduces the stability of the foam. To overcome this, foams stabilized by silica nanoparticles were proposed. Because they are stabilized by solid particles, it is expected that these foams can withstand high temperature environments.

Currently, our study is focused on (i) quantifying the transportability of aqueous nanoparticle dispersions in porous media; (ii) the effects of the properties and volume ratios of the aqueous and non-aqueous phases on the stable foam/emulsion formation; and (iii) quantifying the transportability of nanoparticle-stabilized emulsions in porous media. So far, the experiments have been carried out at ambient conditions employing surrogate non-aqueous phases (toluene, crude oils). Experiments were run to determine the transportability of nanoparticles in porous media. Our results show that nanoparticles can successfully flow through reservoir rock with little to no retention. Rheology tests showed that these solutions have a low viscosity (~3 cp) even for highly concentrated dispersions.

Tests have also been conducted on model emulsions made of liquid hydrocarbon and water to determine stability and viscosity of foams created with surface-treated nanoparticles. Our experiments indicate that nanoparticles can stabilize emulsions for extended periods of time. These emulsions were also stable at temperatures as high as 85° C. Rheology tests on these emulsions showed that their viscosity ranges from 10 cp to several hundred cp.’s.

Columnflood experiments conducted using model emulsions also proved that this class of solid-stabilized emulsions could successfully flow through porous media. The emulsion’s flood profile had a piston-like front, and swept through the entirety of the core. These experiments also showed that the emulsions were stable throughout the experiments. A high percentage of the emulsions were also recovered from the porous media. In addition, viscosity measurements calculated from pressure data showed that the emulsions had an apparent viscosity ranging from 50cp to 70cp.

The insights gained from experiments using model emulsions will allow a more efficient and effective study of CO2/water foams. Presently, experiments at high temperature and pressures are being designed to characterize foams at these conditions. The application of nanoparticle-stabilized CO2 foams can improve the CO2-based EOR techniques and may increase their applicability to a wider range of reservoirs.