Effect of shear on flow properties during placement and on syneresis after placement of a polyacrylamide-chromium acetate gelant

Typical gel polymer treatments to treat fractured rock consist of injecting inline mixed gelant into the reservoir for times usually much longer than the bulk gel time of the gelant. Flow experiments were conducted to determine the effect of shear on the flow properties of the gelant for durations greater than the bulk gel time. Inline mixed gelant was injected through a 1031-ft long tube to simulate a fracture. Flow resistance increased down the tubing to steady values indicating gelation of the flowing system. Similar flow experiments were conducted by injecting preformed gel through the tubing. Flow resistances decreased down the tubing to steady values indicating breakdown of the gel structure. Flow resistances at the steady downstream sections were higher during the injection of inline mixed gelant compared to injection of preformed gel and both were much lower than literature values determined where preformed gel was injected through short fractured rocks and short lengths of tubing. Gel samples underwent syneresis after they were formed during shear flow in the tubing and in a rheometer. Interpretations of flow resistance data from injection of inline mixed gelants and preformed gels in long tubing are presented.