The molecular configuration dimension and the flow performance of Cr3+ polymer gel which was formed from partially hydrolyzed polyacrylamide (HPAM) and Cr3+ were studied by making use of the viscosity measurement, core flow performance test and dynamic light scattering (DLS).

The results showed that Cr3+ polymer gels with different molecular structures could be prepared by changing the gelling conditions such as electrolyte concentration of solvent water, Cr3+ or polymer concentration and so on. If electrolyte concentration of solvent water was high while polymer and Cr3+ concentration were low, the cross-linking reaction between polymer molecule and Cr3+ mainly took place among different chains of the same polymer molecule forming Cr3+ polymer gel with the intra-molecular cross-linking structure. Compared with polymer solution at the same concentration, apparent viscosity of intra-molecular cross-linking Cr3+ polymer gel remained almost unchangeable, but the resistance coefficient and the residual resistance coefficient were much higher while the residual resistance coefficient was higher than the resistance coefficient. Moreover, the molecular configuration dimension (Dh) of the gel was only a little bigger than that of polymer solution so that it still had a favorable compatibility with the rock pore of oil reservoir.

As seen from the statistics of the pilot test, Cr3+ polymer gel presented outstanding profile modification as well as oil displacement. The channeling of high permeability zones of oil reservoir were blocked so well, the injection pressure became so high, and thereby there has already being a great effect on enhancing oil recovery and decreasing water cut.

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