Evaluation of modified cationic starch for impeding polymer channeling and in-depth profile control after polymer flooding

Premature polymer production in large quantities from flooding reservoirs is a serious problem commonly existing in some large oilfields in China. This is owing to polymer channeling through high permeability zones or pore passage. This paper presents a novel modified cationic starch, which can react with partially hydrolyzed polyacrylamide (HPAM) remaining in reservoir formation to form gels in-situ. The obtained gels can reduce polymer channeling and make successive injected water into mid-low permeability zones that achieve the purpose of deep profile control. The rheological property and the gel strength are examined. The singular sand-pack core-flood test results provide experimental evidence that the formed gel system is more effective in plugging high permeability pore passages. Moreover, the parallel core-flood test was conducted to simulate the process of in-depth profile modification in a heterogeneous formation. It has been found that this gel system can significantly enhance oil recovery and effectively reduce water-cut.