| Summary: | Abstract: Aimed at the disadvantages of secondary damage to oil layers caused by the conventional bull-heading water control technique, a thermo-sensitive temporary plugging agent for water control was synthesized by water solution polymerization and applied in the field with a new secondary temporary plugging technique. The optimization and performance evaluation of thermo-sensitive temporary plugging agent were carried out through laboratory experiments. The optimized formula is as follows: (6% − 8%) acrylamide + (0.08% − 0.12%) ammonium persulfate + (1.5% − 2.0%) sepiolite + (0.5% − 0.8%) polyethylene glycol diacrylate. The thermo-sensitive temporary plugging agent is suitable for formation temperatures of 70−90 °C, it has high temporary plugging strength (5−40 kPa), controllable degradation time (1−15 d), the apparent viscosity after degradation of less than 100 mPa(S and the permeability recovery value of simulated cores of more than 95%. Based on the research results, secondary temporary plugging technique was used in a horizontal well in the Jidong Oilfield. After treament, the well saw a drop of water cut to 27%, and now it has a water cut of 67%, its daily increased oil production was 4.8 t, and the cumulative oil increment was 750 t, demonstrating that the technique worked well in controlling water production and increasing oil production. Key words: bull-heading water control technique, thermo-sensitive temporary plugging agent, secondary temporary plugging technique, thermal degradation property, reservoir protection
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