Study on reducing the brittleness of oil well cement by preparing nano-SiO2/epoxy resin composite elastic microspheres based on Pickering emulsion.

Reducing the brittleness of oil well cement is of great significance to improve the durability of the cement sheath under complex loads and prolong the service life of oil and gas wells. To reduce the brittleness of oil well cement, this study used modified nano-SiO 2 as the emulsifier and an epoxy resin/polyamide system as the core material to prepare flexible composite microspheres (ERM-5, ERM-8, and ERM-10) with different core-shell ratios based on the Pickering emulsion method. The morphology, particle size, composition, thermal properties, hydrophilicity, and mechanical properties of ERM were characterized by SEM, laser particle size analyzer, FT-IR, XPS, TGA, interfacial tensiometers, and nanoindentation. The effects of ERM on the compressive strength and elastic modulus of cement stone were studied. The results showed that ERM had a regular spherical structure, and the median particle sizes of ERM-5, ERM-8, and ERM-10 were 30.8, 38.1, and 47.2 µm, respectively. The coating of SiO 2 improved the hydrophilicity and thermal stability of ERM. The elastic modulus of ERM-5, ERM-8, and ERM-10 were 3.04, 3.20, and 3.55 GPa, respectively. More importantly, the incorporation of ERM can effectively reduce the brittleness of oil well cement and improve its strain capacity under load. Among them, the peak strain of the cement sample containing 6% ERM-5 microspheres reached 0.81%, and the elastic modulus decreased to 4.8 GPa, which was 50.5% lower than that of the control sample (9.7 GPa). The pozzolana effect of nano-SiO 2 improved the binding ability of ERM to the cement matrix, which was conducive to the elastic deformation ability of organic core materials, thereby reducing the brittleness of cement. In addition, the debonding of nano-SiO 2 with cement or resin can further dissipate the load stress. Composite microspheres can synergistically exert the performance advantages of inorganic and organic materials, and the simple preparation process and convenient application method make it have good application prospects. [Display omitted] • SiO 2 /epoxy resin microspheres ERM were prepared by the Pickering emulsion method. • The properties of ERM microspheres are controlled by the core-shell ratio. • ERM microspheres effectively reduced the brittleness of cement stone. • The sample containing 6% ERM-5 has the highest deformation ability under load. [ABSTRACT FROM AUTHOR]