| An oilfield in the Ordos Basin is affected by reservoir fractures and high-permeability seepage,which leads to an increase in the water-bearing rise rate of oil wells,and the difficulty of stable production increases year by year.In order to improve the oil recovery of oilfield,this paper were synthesized the polymer microsphere-adjusting agent suitable for the oilfield according to the reservoir conditions of the oilfield,the structure and properties through corresponding characterization methods was studied.Field application tests were conducted.The research results are as follows:(1)Polymer microspheres were prepared by inverse suspension polymerization,using vegetable oil as dispersion medium,Span80/Tween80 as dispersion stabilizer,acrylamide and2-acrylamide-2-methylpropanesulfonicacidaspolymerizationmonomers.N,N’-methylenebispropionamide as a crosslinking agent,and ammonium persulfate-sodium hydrogen sulfite was a redox initiator.Based on the monomer conversion rate and the average particle size distribution of the product,the synthesis process parameters were optimized.The results showed that when the mass ratio of Span80/Tween80 was 3:1,the volume ratio of oil to water was 3.5:1,the concentration of initiator was 0.06%.When the monomer concentration was 9%,the crosslinking agent concentration was 0.20%,the stirring rotation speed was 400 r.min-1,and the reaction temperature was 70°C,polymer microspheres having an average particle diameter of 10.12μm were obtained.(2)The polymer microspheres were characterized and evaluated by infrared spectrometer,scanning electron microscope and optical microscope.The results showed that the prepared microspheres contained amide group,carboxyl group and sulfonic acid group,and the characterization results were consistent with the characteristic groups of the target prod uct;the shape was spherical and many small particles were attached to the surface;theoretically,the temperature resistance reached 205°C,and the thermal stability was better;the pH of the solution is between 6.0 to 8.4,which will not cause corrosion to the injection equipment;it has good hydration expansion and viscoelasticity.(3)The LDY-III core flow experimental device was used to evaluate the migration,profile improvement and plugging performance of polymer microspheres.The results showed that when the microspheres migrate in the porous medium,the pressure of each pressure measuring point will fluctuate greatly,indicating that the migration performance is good;the microsphere will preferentially enter the high permeability layer and block it,so that the subsequent The flow is turned to the low-permeability layer,and the profile improvement rate is 93.30%,indicating that the microspheres have good profile improvement performance for heterogeneous reservoirs;the plugging performance is affected by the microsphere injection concentration and velocity factors when the microspheres are injected.The higher the resistance coefficient and the blocking rate of the porous medium,the greater the resistance coefficient and the blocking rate of the porous medium will decrease when the velocity of the injected microspheres increases.(4)The results of field application of polymer microspheres showed that after the injection of microspheres,the average oil production per area was increased from 1.30t/d to 1.50t/d,and the daily oil production was increased from 66.3t to 76.5t.After 5 months of microsphere adjustment,the cumulative oil increase in the region was 1530t,the accumulated precipitation was 1100m~3,the water content decreased by 3.6%,and the precipitation and oil increase trend were obvious. |
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