Effect of Surface Dilatational Modulus on Bubble Generation in Visualized Pore-Throat Models

Surface Dilatational Properties and Foam Performance of Surfactant-Nanoparticle Foaming System under Ultra-High Salinity

We have studied the surface dilatational properties of aqueous foaming dispersions containing mixtures of silica nanoparticles (Ludox CL) and sulfobetaine (LHSB) in Tahe formation water. The effects of temperature and pH on the surface dilatational modulus and time shift were studied by oscillating drop module (ODM). The ODM results show that the surface dilatational modulus of mixtures of CL and LHSB is large and increases with the decrease of surface area deformation, which results from hydrophobic interaction between adsorbed mixtures. Under test conditions, the Gibbs stability criterion E > σ/2 against foam coarsening is fulfilled. Results of Brewster angle microscopy (BAM) show that an uniform adsorption layer is established at the air-water interface. Temperature and pH-value influence the dilatation modulus of the surface by hydrophobic interaction or adsorption. Time shift has a similar variation trend. This is a surprising feature. It suggests that LHSB adsorbed on CL can respond to surface tension gradient. The time shift difference results from the response of LHSB at different adsorption sites. In addition, sand pack tests show that compared to LHSB, a finer foam was produced by the mixtures CL/LHSB due to the capillary-induced \snap-off". Thus, higher pressure difference and higher oil recovery could be achieved.

Effect of Inorganic Salt on Foam Properties of Nanoparticle and Surfactant Systems

We have studied the effect of NaCl and CaCl2 on phase behavior of foaming aqueous dispersions containing mixtures of silica nanoparticles (Ludox CL) and sulfobetaine (LHSB). At the evaluated ratio, the phase behavior results show that at a low CaCl2 concentration, sedimentation occurs, whereas a stable aqueous dispersion could be achieved when the CaCl2 concentration reaches to 20%. The adsorption experiments show that high concentrations of both NaCl and CaCl2 reduce the adsorption of LHSB to CL. In the CaCl2 dispersion the adsorption decreases significantly and only a few LHSB molecules can be adsorbed on the CL surface. Therefore, without the lower hydrophobicity of LHSB adsorption less CL could adsorbed at the air/water interface. The results on gas permeability show that aqueous dispersions containing mixtures of CL and LHSB show no obvious difference to aqueous systems containing only LHSB. The surface dilatation module of the LHSB and CL system in CaCl2 solution also shows a similar variation to the system with LHSB alone, which is significantly different from the system with 20% NaCl. Finally, foam flow tests in a porous medium show that compared to a 20% CaCl2 dispersion with the LHSB and CL system in 20% NaCl, a finer foam and a higher pressure difference could be achieved.