The general conditions for gel formation by phenolformaldehyde polymer solutions have been examined in studies with three acrylamide polymers. Contrary to an earlier report, polymer crosslinking is found to take place over a wide interval of pH. While the gelation time is relatively insensitive to the concentrations of phenol and formaldehyde or pH, it is strongly influenced by the temperature and the nature of the polymer. These gelants display good injectivity in corefloods and slim-tube experiments at temperatures up to 140°C. On the other hand, the partitioning of phenol into crude oil is found to be a significant issue for the propagation of these gelants. The use of a phenol pre-flush of the formation is shown by numerical modeling to be a potentially viable solution for this problem.

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