A bull-heading water control technique of thermo-sensitive temporary plugging agent

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.