Study on Performance of High Molecular Weight Polymer Gel and Its Application

In workover operations, wellbore fluids go into reservoir formations, resulting in formation damage. This problem can now be resolved with a high molecular weight polymer gel developed by grafting water soluble acrylamide onto the backbones of natural high molecular weight celluloses. Mechanism analyses and performance evaluation of the high molecular weight polymer gel showed that the gel time of the polymer gel is adjustable between 30 min and 600 min, and time for the gel to break is between 1 d and 30 d. The highest temperature at which the polymer gel functions normally is 160℃. Low apparent viscosity (100 mPa·s) renders the polymer gel good injectability. Using crosslinking agent and catalyst, the gel time can be controlled within a reasonable range, and the gelled polymer gel will lose its flowability, forming a high strength gel plug with high pressure bearing capacity. This polymer gel has good contamination resistance ability, and is resistant to contamination from strong acids, strong bases, saltwater of high salinity and crude oils. After operations, the polymer gel can be broken into low viscosity fluid which can then be circulated out of hole. Compared with conventional mechanical sealing and cement sealing methods, polymer gel has much better application prospects in well workover, lost circulation control and water kick control.