Preparation and interfacial behavior of surface-active microspheres for both emulsion stabilization and profile control

Abstract

Polymer microspheres have high swelling ratio, which can be used to improve the heterogeneity of low permeability reservoirs. When combined with a spontaneous emulsifying flooding system, the sweep efficiency of the system can be increased. However, due to its strong hydrophilicity, the conventional polymer microspheres cannot be adsorbed on the oil-water interface and reduce the interfacial tension, so as to improve the stability of emulsion and further improve the oil washing efficiency of spontaneous emulsion flooding. In this paper, surface-active microspheres S-PM are developed by using stearyl methacrylate (SMA) as the surface-active monomer. Compared with conventional polymer microspheres, the microspheres are amphiphilic particles with a swelling particle size of 600 nm, which can improve the stability of emulsions while improving the heterogeneity of low permeability reservoirs. The study of interfacial behavior shows that S-PM can decrease the interfacial tension to 0.005 mN/m by dragging surfactant molecules to the oil-water interface through polar action and increasing the surfactant concentration on the interface, and can increase the interfacial dilatational elastic modulus to 26.5 mN/m by forming a rigid adsorption layer. The emulsion stability analysis and micrographs show that S-PM can be distributed on the surface of the droplet. Due to the decrease of oil-water interfacial tension and the increase of interfacial strength, it is not easy to collide and coalesce, thus improving the emulsion stability. The dewatering rate decreases from 81.6% to 65.4%, and the TSI decreases from 9.7 to 5.3. The profile control results show that after adding S-PM, the spontaneous emulsifying flooding system is suitable for heterogeneous low-permeability reservoirs with permeability ratio below 5. This study expands the function of polymer microspheres, and it is expected to further improve the recovery of low permeability reservoirs by combining surface-active microspheres with a spontaneous emulsion flooding system.