Zwitterionic Silica-Based Hybrid Nanoparticles for Filtration Control in Oil Drilling Conditions

Water-based drilling fluids (WBDFs) that are susceptible to high temperature and saline pollution always exhibit poor ability to control fluid loss and seriously threaten the operation security of oil well drilling; especially, ultradeep well WBDFs that can simultaneously tolerate high salinity and temperature of over 200 °C are difficult to obtain. Herein, a zwitterionic silica-based hybrid nanomaterial (ZSHNM) with a spherical morphology (50–150 nm) was synthesized, and its filtration performance was thoroughly investigated. ZSHNM showed an extraordinary long-term (≥10 months) dispersion stability even at high concentrations in water and possessed remarkable tolerance to high temperature and salinity. Typically, merely adding 2 wt % ZSHNM in WBDFs could achieve an excellent filtration performance even at 240 °C, and with 11 wt % CaCl₂ or 36 wt % NaCl added, it showed the best performance to our knowledge. The results suggested that the sodium bentonite (Na-Bent) dispersion could be well stabilized in the presence of ZSHNM even at high temperature and with the presence of cations. Additionally, the silicate core could improve the thermal stability of ZSHNM, whereas the zwitterionic shell could form complexes with cations and further mitigate the aggregation of Na-Bent particles. Thus, the particle size distribution in WBDFs could be finely regulated similar to that in neat Na-Bent dispersion. Furthermore, given the zwitterionic ZSHNM filled in the micro–nanopores among the Na-Bent particles, a compact and low-permeability filter cake was readily formed and ultimately reduced the drilling fluid loss during the filtration process. This work provided a versatile strategy to address the high temperature and high salinity tolerance of WBDFs synchronously, thereby pioneering a new way to develop high-performance drilling additives for ultradeep and complex wells.