Experimental Study on Charged Nanogels for Interfacial Tension Reduction and Emulsion Stabilization at Various Salinities and Oil Types

Abstract

Nanoparticles have been widely investigated for their mechanisms in enhanced oil recovery, such as rock wettability alternation, oil displacement by disjoining pressure, and the stabilization of emulsion and foam. Nanogels are nanosized cross-linked polymeric particles that have the properties of both nanoparticles and hydrogels. The goal of this study is to investigate the oil–water interfacial behavior in the presence of nanogels, especially the dynamic interfacial tension and the stability of oil-in-water (o/w) emulsions. The nanogels synthesized in this study are able to reduce the oil–water interfacial tension and stabilize the o/w emulsions. The diameter and ζ potential of the charged nanogels are dramatically influenced by brine salinity, whereas the neutral charged nanogels are barely affected by salt. The synthesized nanogels have been stable in distilled water and brines at room temperature for more than 60 days. The dynamic interfacial tension results show that the nanogels are able to reduce the oil–water interfacial tension to as much as 1/30 of the original value. In addition, the interfacial tension reduction is more significant at a higher salinity (ranging from 10 000 to 50 000 ppm NaCl concentration). The emulsion stability results demonstrated that the stability of emulsified oil drops was controlled by both the strength of the adsorbed nanogel layers and the interactions among oil drops. The core flooding experiments have indicated the residual oil can be fragmented and produced in the o/w emulsion state. In addition, the diameter of emulsified oil drops in effluent is inversely proportional to the shear rate. The salt-dependent interfacial tension and emulsion stability indicated that the appropriate charged nanogel can be a promising candidate for enhanced oil recovery.

Surface Wettability-Switchable Janus Fiber Fragments Stabilize Pickering Emulsions for Effective Oil/Water Separation

“…It was indicated that nonspheric emulsifiers had a better package efficiency and heterogeneous resistance than JPs, which was ascribed to their higher degree of rotational bending and larger adsorption areas of JFs on the droplet surface . In addition, the water–oil interfacial tension in the presence JFs was 12 mN/m, which was lower than that of JPs-stabilized emulsions (15 mN/m), indicating an easier formation of emulsions by JF emulsifiers . Compared with a point-to-point conformation of JPs, JFs showed a side-to-side conformation between oil and water phases, which caused a better heterogeneous resistance .…”

“…46 In addition, the water−oil interfacial tension in the presence JFs was 12 mN/m, which was lower than that of JPs-stabilized emulsions (15 mN/m), indicating an easier formation of emulsions by JF emulsifiers. 47 Compared with a point-to-point conformation of JPs, JFs showed a side-to-side conformation between oil and water phases, which caused a better heterogeneous resistance. 48 In addition, due to the formation of side-to-side conformation, JFs could slide better along the major axis while the vertical and rotational translations were limited.…”

The Effect of Ionic Strength on the Formation and Stability of Ovalbumin–Xanthan Gum Complex Emulsions

“…The composite emulsions reached their lowest interfacial tension value at a NaCl concentration of 0.08 mol/L, which may be attributed to the disordered structure of the protein at the oil-water interface led to a rapid change in its conformation with increasing NaCl concentration, which reduced the interfacial tension and produced a lower equilibrium interfacial tension over time [38]. Secondly, due to the hydrophilicity of OVA, the addition of salt ions significantly reduced the dispersion of the emulsion extremely low, which led to the gradual stabilization of the composite solution and resulted in lower energy of the entire system [39]. Furthermore, the inclusion of NaCl, comprising sodium and chloride ions, reduced the electrostatic repulsion between charged emulsions at the oil-water interface.…”

Research Progress on Functionalized Polymer Microspheres for Deep Profile Control and Flooding

“…Based on the results of plugging and displacement experiments, the oil displacement mechanism of polymer microspheres can be analyzed. Parameters such as interfacial tension, structural separation pressure, wettability, emulsification, and sweep efficiency are also subjected to relevant testing and analysis [29,30].…”