Abstract:

To the problem of gel breaking prematurely in fracturing operations，encapsulated breaker is produced with ammonium persulfate as the core and appropriate polymer materials as the coat by media dispersion and phase separation.Polyvinyl alcohol （PVA） and ethylene vinyl acetate copolymer （EVA） is selected as the coat materials by experimentation and comparing.The preparation technology is studied by orthogonal experiment.The result shows that the performance of encapsulated breaker can be influenced by the stirring rate，temperature，mass ratio of coat and core materials，mass fraction of coat materials in solution and dispersant mass fraction.For the encapsulated breaker with coat materials of PVA，the optimal preparation conditions are the temperature is at 25℃，the stirring rate at 270r/min，the mass ratio of coat and core material at 2∶8，and the dispersing agent mass fraction at 1%.For the encapsulated breaker with coat materials of EVA，the optimal preparation conditions are the temperature is at 25℃，the stirring rate at 300r/min，the mass fraction of coat materials in solution at 5%，and the dispersing agent at 2%.

Key words: fracturing liquids, encapsulated breaker, delayed release, preparation, dispersion and dispersing agent