Preparation Of Temperature-resistant And Salt-resistant Slow-swelling Microspheres By Inverse Emulsion Polymerization And Its Performance Evaluatio

Inverse emulsion polymerization,polymer microspheres,temperature-resistant and saltresistant anti-swelling inverse emulsion polymerization has the advantages of relatively stable emulsion system,the uniform particle size distribution of prepared microspheres,and no need to add stabilizer in the process.The polymer microspheres have the characteristics of "access,migration,blockage and long life",which can gradually migrate to the action position with the migration of the injected fluid,and complete the plugging of the pore throat through relevant physical and chemical actions.At present,the microsphere system has some shortcomings,such as poor temperature resistance,salt resistance and slow expansion resistance,and poor plugging ability.In this paper,a series of experiments and researches have been carried out from the two aspects of the selection of inverse emulsion system and the preparation of polymer microspheres,and a kind of temperature-resistant and salt-resistant polymer microspheres with slow expansion has been prepared,and the following conclusions have been obtained:In terms of the selection of an inverse emulsion system,acrylamide(AM)was selected as the main monomer and 2-acrylamide-2-methyl-propane sulfonic acid(AMPS)and acrylic acid(AA)as the auxiliary monomers to improve the anti-temperature,anti-salt and anti-swelling properties of the microspheres.After comprehensive consideration of compatibility,boiling point and cost,kerosene was selected as the oil phase of the reverse emulsion.In terms of HLB value selection,the experiment was carried out with the selected complex system of SPAN 80/TWEEN-80,and the results showed that the inverted emulsion with HLB value in the range of 5.2-6 had better stability.Through further experiments,the compound system of SPAN-80/TWEEN-60 was optimized,and the dosage of the emulsifier was 10 g.Moreover,the mass ratio of emulsifier was m(SPAN-80):m(TWEEN-60)=87:13,which had the best effect,and the corresponding HLB value was 5.626.In the preparation of polymer microspheres,2,2’azobis[2-methylpropionamidine]dihydrochloride(AIBA)was the best initiator.The suitable range of initiator dosage,crosslinking dosage,pH value,reaction temperature and stirring rate was determined by a single factor experiment,and the final reaction conditions were optimized by orthogonal experiment.To prepare high-quality polymer microspheres,the optimized reaction conditions were:fixed oil phase kerosene,kerosene mass of 55 g,water mass of 50g,monomer total mass of 16 g,monomer mass ratio of AM:AMPS:AA=6:3:1,and use sodium hydroxide solution to adjust the pH of water phase to 7.The mechanical stirring speed was 700rpm,stirring for 30min.The compound system SPAN-80/TWEEN-60 was adopted,the mass ratio of emulsifier was m(SPAN-80):m(TWEEN-60)=87:13,and the mass of emulsifier was 10 g.In the preparation process,the stirring rate was 350r/min,the initiator dosage was 0.014%,the crosslinking agent dosage was 5%,the temperature was 50℃,and the reaction lasted 3h.The product was AM-AMPS-AA copolymer.Scanning electron microscopy(SEM)showed that the dry powder of the microspheres was spherical and had an average particle size of 1-3 μm.The median particle size of the microspheres in water is 9.054 μm,according to the analysis results of the laser particle size analyzer.The results of the thermogravimetric experiment showed that the mass of the powder was lost by 50%at 384℃.In the water absorption expansion experiment,the microspheres can also maintain a certain expansion performance in the solution of 100000mg/L at 80℃.The maximum expansion factor was reached after 10days in an oven at 80℃ with a salinity of 30000mg/L.At the same time,1 g microsphere powder was dissolved in 20ml pure water or sodium chloride solution of 100000 salinity and placed in an oven at 80℃ for 72 h.Core displacement experiments show that the microspheres can enter the cores with liquid permeability between 80 mD to 373 mD and complete migration in these cores,maintaining a high plugging efficiency,and the maximum plugging efficiency can reach 84.21%..