A high temperature resistance and hyper‐dispersed nanoparticle grafted by multi‐monomer via in‐situ polymerization: Preparation, characterization, and its imbibition performance

Abstract

AbstractIn recent years, the excellent cleaning‐oil capacity of nanofluid has attracted extensive attention and it has been widely used in oilfields as an imbibition agent. To solve the poor dispersion stability of nanoparticles in high‐temperature and high‐salt reservoir, this paper has prepared a hyper‐dispersed nanoparticle, polymer grafted nanosilica (PNS) that is anti‐salt monomer and anti‐temperature monomer simultaneously grafting on the surface of nanosilica via in‐situ polymerization reaction. Its imbibition performance has been discussed. Results show that (1) The two monomers are all successfully grafted on the surface of nanosilica via optimization of in‐situ polymerization reaction conditions. This hyper‐dispersed nanoparticle has 14.5% final grafting rate, approximately 18 nm in particle size, and −41.2 mV of zeta potential; (2) PNS fluid has excellent dispersion stability and its grain size has no obvious change in 20 wt.% of NaCl or 4 wt.% of CaCl2 fluids at room temperature (25°C), as well as in 18 wt.% of NaCl or 4 wt.% of CaCl2 fluids at 130°C after 1 week; (3) Crude oil–water interface tension can be decreased and the hydrophilicity is significantly boosted by this PNS fluid. Meanwhile, the 10−3 mN/m of interface tension can be obtained and the contact angle of water phase is decreased to 12.8° by surfactant erucamide propyl hydroxysulfobetaine (EHSB) synergizing with PNS fluid; (4) Oil recovery efficiency replaced by PNS in surfactant fluid has reached 39.3%. That is mainly because the hyper‐dispersed nanoparticle provides a stronger spreading force to enhance the efficiency of cleaning oil.