Solid-shelled microspheres loaded with solvent as diluents for extracting blockages by heavy-oil and asphaltene precipitates

A novel type of solid-shelled microspheres was prepared by emulsion templating technique through layer-by-layer self assembly. The regulation controlled by different payloads, surfactants, 3-aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) ratio produced three solid-shelled microspheres with various morphology, sizes, shell thicknesses and brittleness. Such microspheres can be considered as diluent-loaded eggs that can be cracked when forced between narrow rock surfaces or against blocking fluid flow particles. The structural characteristics, size distribution, stability, breakable and release behavior of three payload-in-silica microspheres were investigated by optical microscopy techniques and scanning electron microscopy (SEM) technique, dynamic light scattering (DLS), zeta potential, and ultraviolet-visible (UV-vis) spectroscopy. The results indicated that these three microspheres were relatively uniform in size (1-5 μm) and had a smooth surface with shell thicknesses of 40-120 nm, which also possessed excellent stability. Yet the brittleness of silica shell was obviously different for three solid-shelled microspheres, in detail, the silica shell of toluene microspheres was more brittle and easier to be ruptured than hexane microspheres under external hydrodynamics forces. Sand column tests revealed that the easy-broken toluene-in-silica microspheres prepared from tween-80 template matched the pore throat of reservoir better and achieved higher heavy oil recovery efficiency (94.60%). Such breakable microspheres can provide a selective and targeted diluting approach to extract blockages by heavy-oil and asphaltene precipitates.