Studies On Synthesis And Properties Of Magnetic Polymer Microspheres As Flooding Profile Control And Water Plugging Materials

Deep profile control and water plugging technology is a newtechnology used for water injection oilfield in the development of middleor high water content. Polymer microspheres technology has manyadvantages. It can meet the special requirements of "able to inject, able toblock, able to move", and achieve deep profile control and waterplugging step by step. Adding inorganic magnetic components in thepolymer microspheres will make the magnetic polymer microspheres hastwo application features. One is used in the production wells as magneticwater plugging agent to enhance oil recovery. The other is used ininjection wells as profile control displacing agent. If the microspheres aresqueezed into the oil layers and carried out with produced fluid, magneticseparation can be done.In this paper we synthesize a novel magnetic polymer microspherefor profile control and water plugging. This microsphere is composited with core-shell Fe₃O₄@SiO₂inorganic magnetic components andPAMAA or PAM organic components. We also test its swelling capacity,rheological property, plugging property and magnetic separation. Themain studied contents and conclusions are as follows:1. The magnetic Fe₃O₄nanoparticles are synthesized by thecoprecipitation. Then their surface is coated with SiO₂to form core-shellFe₃O₄@SiO₂particles. And the Fe₃O₄@SiO₂particles are modified byKH-570. Finally, we use dispersion polymerization in the presence ofFe₃O₄@SiO₂magnetic particles with acrylamide and acrylic acid oracrylamide only as the monomer to obtain two kinds of magnetic polymermicrospheres named PAMAA/Fe₃O₄@SiO₂and PAM/Fe₃O₄@SiO₂.Characterizations by scanning electron microscope, fourier transforminfrared spectrometer and vibrating sample magnetometer prove that theprepared PAMAA/Fe₃O₄@SiO₂and PAM/Fe₃O₄@SiO₂microspheres aremicro sizes. They form a good composited structure and are bothsuperparamagnetic.2. We study the effects of solution salinity, swelling temperature andswelling time on the swelling properties of the magnetic polymermicrospheres. Both the PAMAA/Fe₃O₄@SiO₂and PAM/Fe₃O₄@SiO₂microspheres have strong temperature and salt resistance and stablestructure. After swelling for12days, the particle size can be inflated toabout six times of the initials. 3. Rheological property of the magnetic microspheres is tested byrheometer. When the shear rate is fixed at600s^-1, the dispersion system ofPAMAA/Fe₃O₄@SiO₂microspheres is time dependent fluid and belongsto shock-condensable fluid. But that of PAM/Fe₃O₄@SiO₂microspheresis time independent fluid. They both express as pseudo plastic fluids atlow shear rate, express as rose plastic fluids at middle shear rate, andexpress as approximate Newtonian fluids at high shear rate.4. Plugging property of the magnetic polymer microspheres isanalyzed by microporous membranes. The plugging ability ofPAMAA/Fe₃O₄@SiO₂composite microspheres shows a weakening trendafter the first increasing trend with the increase of swelling time. And it isthe best when swelling of4days.5. We use a magnet to test the magnetic separation of the magneticpolymer microspheres. Results show that the microspheres can be easilyseparated from dispersion system by an external magnetic field.