Research and Application of Anti-Emulsification Oil Washing Workover Fluid Technology

In order to solve the reservoir pollution during the workover operation in the complex fault block oilfield of Dagang Oilfield, especially the high pour point oil blocks represented by Xiaoji and Duanliubao, multiple damages such as water sensitivity, crude oil emulsification, and retention coexist, leading to serious reservoir pollution problems, Through the research of high-efficiency pour point depressing, wetting and dispersing technology, a technical system of anti-emulsification oil washing workover fluid is formed. The results show that the technology can effectively reduce the freezing point of crude oil by more than 9 ℃, and the oil washing rate is increased from 60.7% to 90.2%, achieving the dual effect of not only cleaning the wellbore to ensure the smooth operation, but also increasing the production recovery rate. This technology has been applied 20 wells in Dagang Oilfield. The average production recovery rate of applied wells has been increased from 77.7% to 97.6%, and the average recovery period is 2.8 days, which shows that the reservoir protection effect is significant.