| Nowadays,most oil fields in China have entered the mid to late stage of water injection development.In response to the problems of high water content of produced liquid and low oil and gas recovery rate that occur on site,it is necessary to continuously innovate and develop profile control and displacement technology to meet the requirements of oilfield precipitation and oil increase.Among them,the core shell polymer micro-sphere profile control and displacement technology,due to the "core/shell" double layer structure of micro-spheres,has strong temperature resistance,salt resistance,shear resistance,and small initial particle size With excellent swelling performance and other characteristics,it has great potential for application in the field of deep profile control and flooding in oil fields,becoming a key direction for development in this field.In view of the problems that conventional polymer micro-spheres are easy to be sheared and damaged during formation profile control and flooding operations and the low plugging strength,this research adopts reverse micro lotion polymerization,takes core cationic monomer,acrylamide and acrylic acid as monomers,ammonium persulfate as initiator,Span80 as emulsifier,and white oil as dispersion medium to synthesize a system with high effective ingredient content,excellent swelling performance,and high shear strength Core shell polymer micro-spheres with good profile control and displacement performance.And the monomer conversion rate was used as the evaluation index to optimize the factors affecting the preparation system,such as reaction initiation temperature,reaction time,monomer water solution addition method,initiator dosage,and stirring speed.At the same time,to demonstrate the feasibility of the prepared micro-spheres in deep oil reservoir profile control and flooding applications,the physical properties,swelling ability,and shear resistance of the micro-spheres were evaluated.The characterization and evaluation results show that the synthesized product exhibits a micro basic spherical shape with an initial particle size of 0.31 μ Polymer micro-spheres with core-shell structure;The mother liquid of the micro-spheres is a milky white semi transparent liquid,and the dry powder particles of the micro-spheres are white and delicate solid powder.At a temperature of 25 ℃,the average density is 1.0179g/cm3,and the viscosity of the mother liquid is404.9m Pa · s,which has good dispersibility in water;The effective content of the system is 35.38%;At the same time,the micro-spheres exhibit good swelling performance and possess considerable shear and compression resistance.Through indoor physical simulation displacement experiments,relevant research was conducted on the injectability,sealing ability,profile improvement ability,and oil recovery ability of core-shell polymer micro-spheres.Injectivity experiments have shown that micro-spheres have good injection ability for simulating artificial rock core flooding,and the overall injection pressure shows a trend of increasing with decreasing core permeability,increasing solution concentration,and increasing injection rate;The research on sealing ability shows that micro-spheres have good core sealing ability,with a maximum sealing rate of 88.43%.In terms of profile control and displacement performance,the results of dual tube parallel experiment research show that the core-shell polymer micro-sphere needle has good profile improvement ability for artificial cores with different permeability ranges.After profile control with the micro-sphere system,the heterogeneity of the parallel core is improved,and the highest experimental profile improvement rate can reach 92.66%;In terms of oil displacement and recovery,core-shell polymer micro-spheres have better oil displacement and recovery performance when used to enhance oil recovery in reservoirs,with recovery and recovery rate increases of 65.54% and 20.53%. |
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