Polymer flood has been being used to provide a valuable tool for in-depth blockage of high permeability regions of the reservoirs in the Daqing oil field, where more than fifty thousand tons of polymers had been injected into reservoir for each year. But heterogeneity inside the reservoir is very serious in some areas and has caused channlling of polymer solution through high permeable zones, which not only wasted a lot of polymer but also affected the volumetric sweep.
The colloidal dispersion gels (CDG) were made up of low concentrations of polymer, aluminum citrate and additive in water, and combined with polymer solution during polymer flood for in-depth blockage of high permeability regions1,2,3. This paper provides a study of the performances and characteristics of the gels that were made up of aluminum citrate, produced water and polymer made in the Daqing oil field. The parameters used to evaluate performances and characteristics of the gels in laboratory include resistance factor, residual resistance factor, viscosity, elasticity, and polymer molecular texture and flood efficiency. The experiment results showed that the cross-linking reaction among a few polymer molecules or inside a molecule had taken place, which caused performance difference between the gel and polymer solution, and the best gels can be formed with a polymer: aluminum: additive S ratio of 100: 1: 25. The cost of the gels formed with the above-mentioned ratio was below 5 dollars /m3, which was almost the same as polymer solutions. According to these experimental results, two pilot test units with seven injection wells have been selected in the central part of the oil field, in which there are three central injection wells.