Preparation Of Modified Halloysite Nanofluid And Study On Its Oil Displacement Performance

At present,with the rapid growth of global oil demand,the exploitation of low permeability reservoirs has increasingly become the focus of research.Due to the useful characteristics such as changing rock wettability,reducing interfacial tension,nanoparticles size close to the average radius scale of pore throat,nanofluid can further improve the recovery of low permeability reservoirs.In this paper,halloysite nanotubes were modified by coating modification and surfactant modification to improve their dispersibility.And then the effect of modified halloysite nanofluids on oil recovery efficiency was studied.The main work includes the following two aspects:(1)Coating modification:In the alcohol-water mixed solvent system,using ammonia as catalyst and tetraethyl orthosilicate as silicon source,nanosilica(SiO2)was coated on the surface of halloysite nanotube(HNTs).The dispersion stability of halloysite nanoparticles before and after modification was investigated.It was proved that silica coating can improve the surface charge of halloysite nanoparticles,increase the electric repulsion force,resulting in improving the dispersion stability.At the same time,HNTs/SiO2 nanofluids increase the water viscosity and have the ability to reverse the surface wettability of oil-wet solid,which can effectively improve oil recovery.(2)Surfactant modification:By measuring the dispersion stability,oil-water interfacial tension and emulsifying effect of different types of surfactant(cationic surfactant,anionic surfactant,nonionic surfactant)modified halloysite particles,it was found that the dispersion stability of surfactant modified halloysite nanotubes was improved.It screened out halloysite nanoparticles modified by APG0810,a non-ionic surfactant with alkyl glycosides,have the best ability to reduce interfacial tension.The halloysite nanoparticles modified by DTAB have the best emulsification effect.Based on this,the composite nanoparticles(H-GDBB)were obtained from modified halloysite nanoparticles by self-made sugar-based cationic non ionic surfactant(GDBB).The stability of Pickering emulsions was determined by water absorption,droplet size and viscosity of emulsion.It was concluded that the wetting neutral H-GDBB nanoparticles could reach the most stable emulsion.Experiments show that H-GDBB nanofluids can also reduce the interfacial tension between oil and water,reverse the surface of oil-wet solid to be water-wet,and improve the oil recovery.