Plug Remover for Polymer Gel Based on Phase Transfer Catalytic Degradation

In order to rapidly degrade and disperse three-dimensional network cross-linked polymer gel causing formation blockage, a non-redox targeted plug remover for polymer gel was developed with polarizing agent(polyether amine 1000), catalyst(vanadium(IV)oxy acetylacetonate), substitution agent(hydroxypropyl tetrahydropyrantriol, diethylenetriamine pentamethylphosphonate) and solubilizing dispersant (18-crown-6, trimethylsilyl ethanol) as the main components. The degradation and dispersion efficiency of polymer gel, core permeability recovery rate and corrosion resistance of the plugging remover were studied. The results indicated that the plug remover had a good degradation and dispersion effect on the polymer gel. At the  temperature of 60℃, the 10% plug remover could make the degradation rate of the micro-nano gel particles with a particle size of 0.5—100um synthesized with acrylamide and acrylic acid as the main monomers more than 92%. The degradation rate of the polymer gel particles increased with the extension of time, reaching more than 90% after 72 h. The recovery rate of plug removal by core displacement was 87%, which could effectively remove the blockage caused by gel particles in the formation. At the temperature of 60℃, the corrosion rate of 10% plug remover on tubing and casing was 0.4898 g/(m2·h), which was lower than that of conventional plug remover system in oilfield, and could ensure the safe construction on site. The field test results showed that the plug remover had a higher success rate of more than 90%, an average daily injection increase of 16.3 m3 per well, a decrease of 3.2 MPa in injection pressure, an effective period of more than 200 days, and a cumulative injection increase of more than 3920 m3. The increasing injection effect of the plug remover was good, which was suitable for the application of under-injection wells caused by polymer gel particle profile control and flooding.