Research On Silica Nanoparticles Modified With Hydrophilic Polymers

Organic-inorganic hybrid nanoparticles exhibit both properties of inorganic and organic nanoparticles,that have important potential applications in solving wellbore instability problems by plugging the nano pores of the shale formations.In this thesis,a series of hydrophilic polymer modified silica nanoparticles were prepared by a copolymerization method,and the dispersibility,compatibility,and plugging performance of these nanoparticles were studied.The main works of this thesis are as follows:(1)With tetraethyl orthosilicate as silicon source,50-120 nm silica nanoparticles and 3-methacryloxypropyltrimethoxysilane modified silica nanoparticles were prepared by a sol-gel method,then poly(acrylic acid)modified silica nanoparticles were prepared by a copolymerization method.The poly(acrylic acid)modified silica nanoparticles have a good dispersibility in NaCl and MgCl2 aqueous solutions with a same critical salt concentration of 6%.While in Al2(SO4)3 aqueous solutions,the poly(acrylic acid)modified silica nanoparticles coagulate and precipitate quickly when the Al2(SO4)3 concentration is above 0.5%.The poly(acrylic acid)modified silica nanoparticles showed good compatibility with polyacrylamide(PAM),carboxymethyl cellulose(CMC)and sulfonated phenolic resin(SMP-2).The results of plugging test indicate that the poly(acrylic acid)modified silica nanoparticles have an excellent plugging performance on man-made filter cakes and the plugging performance enhanced as the concentration of the nanoparticles increase.(2)Poly(sodium-p-styrenesulfonate)modified silica nanoparticles were prepared by a copolymerization method.The poly(sodium-p-styrenesulfonate)modified silica nanoparticles have a good dispersibility in NaCl and MgCl2 aqueous solutions with a critical salt concentration of 15%and 12%respectively.While in Al2(SO4)3 aqueous solutions,the poly(sodium-p-styrenesulfonate)modified silica nanoparticles coagulate and precipitate quickly when the Al2(SO4)3 concentration is between 0.5%-2%.The poly(sodium-p-styrenesulfonate)modified silica nanoparticles showed good compatibility with polyacrylamide(PAM),carboxymethyl cellulose(CMC)and sulfonated phenolic resin(SMP-2).The results of plugging test indicate that the poly(sodium-p-styrenesulfonate)modified silica nanoparticles have an excellent plugging performance on man-made filter cakes and the plugging performance enhanced as the concentration of the nanoparticles increase.(3)Poly(2-crylamide-2-methylpropanesulfonic acid)modified silica nanoparticles were prepared by a copolymerization method.The poly(2-crylamide-2-methylpropanesulfonic acid)modified silica nanoparticles have a good dispersibility in NaCl and MgCl2 aqueous solutions with a critical salt concentration of 21%and 12%respectively.While in Al2(SO4)3 aqueous solutions,the poly(2-crylamide-2-methylpropanesulfonic acid)modified silica nanoparticles coagulate and precipitate quickly when the Al2(SO4)3 concentration is at 0.5%.The poly(2-crylamide-2-methylpropanesulfonic acid)modified silica nanoparticles showed good compatibility with polyacrylamide(PAM),carboxymethyl cellulose(CMC)and sulfonated phenolic resin(SMP-2).The results of plugging test indicate that the poly(2-crylamide-2-methylpropanesulfonic acid)modified silica nanoparticles have an excellent plugging performance on man-made filter cakes and the plugging performance enhanced as the concentration of the nanoparticles increase.(4)Poly(N-isopropylacrylamide)modified silica nanoparticles were prepared by a copolymerization method.The poly(N-isopropylacrylamide)modified silica nanoparticles have a poor dispersibility in NaCl,MgCl2 and Al2(SO4)3 aqueous solutions with a same critical salt concentration of 0.5%.The poly(N-isopropylacrylamide)modified silica nanoparticles showed good compatibility with polyacrylamide(PAM),carboxymethyl cellulose(CMC)and sulfonated phenolic resin(SMP-2).The results of plugging test indicate that the poly(N-isopropylacrylamide)modified silica nanoparticles have an excellent plugging performance on man-made filter cakes and the plugging performance enhanced as the concentration of the nanoparticles increase.(5)Poly(methacrylatoethyl trimethyl ammonium chloride)modified silica nanoparticles were prepared by a copolymerization method.The poly(methacrylatoethyl trimethyl ammonium chloride)modified silica nanoparticles have a good dispersibility in NaCl,MgCl2 and Al2(SO4)3 aqueous solutions with a critical salt concentration of 16%,28%and 28%respectively.The poly(methacrylatoethyl trimethyl ammonium chloride)modified silica nanoparticles showed good compatibility with polyacrylamide(PAM),carboxymethyl cellulose(CMC)and sulfonated phenolic resin(SMP-2).The results of plugging test indicate that the poly(methacrylatoethyl trimethyl ammonium chloride)modified silica nanoparticles have an excellent plugging performance on man-made filter cakes and the plugging performance enhanced as the concentration of the nanoparticles increase.