Influencing factor and cross-linking performance evaluation of asynchronous cross-linking profile control and flooding system

To solve some problems of the common used cross-linking polymer system such as shorter gel time and lover gel strength, an asynchronously cross-linking polymer profile control and flooding system, which consisted of partially hydrolyzed polyacrylamide, organic chromium, organic phenolic resin, was developed. The cross-linking property, influencing factors, profile control and flooding performance were tested via gel strength tested and scanning electron microscopy analysis. The results showed that the course of reaction between polymer and organic chromium/organic phenolic resin, belongs to asynchronous reaction, two steps are presented with the increase of gel strength and the gel which formed through asynchronous reaction would not dehydrate and its microstructure was tightly. Gel showed high strength when Na+ concentration was below 35 000 mg/L, Ca2+ concentration was below 1 500 mg/L, temperature was between 50 ℃ and 90 ℃ and pH was in the range of 4 and 7. The profile control and flooding core flooding experiment showed that the plugging rate of asynchronous cross-linking polymer system was 95.33% and it had good performance of selective water shut off. The gel time of asynchronous cross-linking polymer system was longer than 300 h when temperature was below 60 ℃. The system could be used to deal with deep profile control and flooding problem of the deep layer.