Abstract
Suffering from serious rod-tubing eccentric wear, polymer-flooding wells usually have an average maintenance cycle of only 2-3 months. Analysis indicates that since the wellbore fluid causes a relatively large friction to the pump and rod in polymer-flooding production wells, rod-string buckling is likely to occur during the down-stroke. In addition, the normal force difference will make collision between rod and tubing more frequently, which in turn aggravate the rod fatigue and rod-tubing wear. A special downhole pump newly developed and rod-string optimization for polymer-flooding production wells together work well in reducing the system load, rod-tubing contact and wear. The rod-tubing wear of PCP wells is reduced through structure parameter optimization, application of equal-wall thickness PCP, pump-type optimization, etc. After a series of remedial measures and scale application, the failure rate of artificial lift systems in polymer-flooding has been significantly reduced, and the mean-time-between-failure (MTBF) increased to more than a year and a half in the study area. This technology is of great significance for the wide application of polymer-flooding and further improvement of tertiary oil recovery profit.
