Slow gelation of titanium(IV) with partially hydrolyzed polyacrylamide. Crosslinking reaction and gel properties

The gelation of metallic crosslinking agent titanium(IV) (Ti(IV)) with partially hydrolyzed polyacrylamide (HPAM) is studied. Factors effecting the crosslinking reaction are discussed and the dynamic properties of gel are examined. The results indicate that crosslinking of TI(IV) with HPAM is delayed at low concentrations of polymer and the titanium tartrate. The gelling of Ti(IV)-HPAM is a strong function of titanium/tartaric acid molar ratio, HPAM concentration, initial solution pH value, solution salinity, and hydrolysis degree of HPAM. The gel strength depends on Ti(IV) concentration in a particular way, after a maximum Ti(I) concentration is reached gel strength decreases. The salt NaCl can accelerate the gelling rate of Ti(IV)-HPAM. The crosslinking mechanism of Ti(IV) with HPAM is proposed. Ti(IV)-HPAM gel can hold its strength at moderate temperature (50 degreesC) for a long time which is suitable to be used in a moderate temperature oil reservoir.