Study and Application of Compound Plugging Removal Workover Fluid in Offshore Injection Polymer Oilfield

In order to solve the polymer plugging problem in Bohai injection oil field, a compound plugging removal workover fluid system was developed to remove the polymer blockage in the near-well area and restore the productivity of the oil well. Compound plugging removal workover liquid is composed of main agent oxidant and auxiliary agent cleaning agent and chelating agent. Static dissolution and dynamic core displacement experiments were carried out to evaluate the polymer plugging and dissolution ability of composite plugging workover fluid. Laboratory experiments show that the system has a good ability of polymer degradation, oil washing and metal cation chelation, and can completely dissolve the organic components in the oil-bearing polymer scale in 24 hours. Dynamic displacement experiments show that the permeability recovery rate of polymer damaged cores is up to 96% after the injection of composite plugging removal workover fluid system. The system has been applied to the well workover operation in the injection oil field, and it has the obvious ability to extract liquid and increase oil, which provides a strong support for the offshore injection oil field to improve the oil well productivity in the window period of the workover operation.