Aqueous Foam Stabilized by Hydrophobic SiO₂ Nanoparticles using Mixed Anionic Surfactant Systems under High‐Salinity Brine Condition

Abstract

A primary concern of surfactant‐assisted foams in enhanced oil recovery (EOR) is the stability of the foams. In recent studies, foam stability has been successfully improved by the use of nanoparticles (NP). The adhesion energy of the NP is larger than the adsorbed surfactant molecules at the air–water interface, leading to a steric barrier to mitigate foam‐film ruptures and liquid‐foam coalescence. In this study, the partially hydrophobic SiO2 nanoparticles (SiO2‐NP) were introduced to anionic mixed‐surfactant systems to investigate their potential for improving the foamability and stability. An appropriate ratio of internal olefin sulfonate (C15‐18 IOS) and sodium polyethylene glycol monohexadecyl ether sulfate (C32H66Na2O5S) was selected to avoid the formation of undesirable effects such as precipitation and phase separation under high‐salt conditions. The effects of the NP‐stabilized foams were investigated through a static foam column experiment. The surface tension, zeta potential, bubble size, and bubble size distribution were observed. The stability of the static foam in a column test was evaluated by co‐injecting the NP‐surfactant mixture with air gas. The results indicate that the foam stability depends on the dispersion of NP in the bulk phase and at the water–air interface. A correlation was observed in the NP‐stabilized foam that stability increased with increasing negative zeta potential values (−54.2 mv). This result also corresponds to the smallest bubble size (214 μm in diameter) and uniform size distribution pattern. The findings from this study provide insights into the viability of creating NP‐surfactant interactions in surfactant‐stabilized foams for oil field applications.

Evaluation of Silica-Based Nanofluid Foam in Waxy Oil Recovery and Its Role in Mitigation of Surfactant Loss

“…Emrani and Ibrahim explained that the nanoparticles could be adsorbed and minimized due to the contact area between the gas and liquid phase acting as a barrier to prevent foam bubbles from collapsing. As mentioned earlier, the dispersed SNPs in the solution could prevent gas diffusion through the film lamellae, resulting in higher foam stability . When the foams became stable, an increase in the differential pressure was observed.…”

“…Later, the foam collapsed with time and reached its half-life at 15 min. With SNPs, the initial foam height slightly decreased, which could be caused by less available surfactants to generate foams due to the competitiveness of the surfactant adsorption onto the surfaces of SNPs and at the air–water interface . In contrast, adding SNPs significantly enhanced foam stability, by which the half-life with adding 1000 ppm SNPs was prolonged to 35 min, and only slightly increased to 38 min when the concentrations of SNP increased to 2500 and 5000 ppm.…”

“…First, the SNP–surfactant foam systems could generate more stable foams than the system without SNPs, suggested by the higher foam stability for the SNP–surfactant system in the foam generation by the shaking test (see Table and Figure ). This was attributed to the presence of SNPs at the foam lamellar to prevent the gas transfer and, consequently, prevent the collapse of bubble walls . As the SNP concentration increased, a higher pressure drop was observed.…”

“…Second, oil droplets may form an emulsion with the surfactant in the foam films, providing fewer surfactant molecules at the gas–water interfaces and accelerating the foam drainage; hence, the foams collapse faster . However, in the presence of nanoparticles, the added nanoparticles may disperse at the gas–water interface of the foam lamellae and reduce the gas–water interfacial area, leading to less gas diffusion through the film lamellae; thus, the foam stability increases.…”

An experimental investigation of dynamic viscosity of foam at different temperatures

“…In foam systems with nanoparticles (SiO 2 NPs), NPs disperse at the gas-liquid interface, as shown in Figure 11c. It is expected that, this creates electrical double layers that cause further repulsions between NPs and making the foam lamellae thicker, also this can help to overcome the capillary pressure and prevents gas diffusion from neighbouring bubbles [12,64]. Moreover, the presence of the NPs at the gas-liquid interfaces results in a reduction in their surface tension [65,66].…”