A Study On The Polymer Solution Preparing With Fresh Water And Diluting With Produced Water

In the process of displacement of oil by polymer solution, the viscosity and viscoelasticity of polymer solution are vital to displacement efficiency. Low TDS fresh water is generally used to prepare polymer solution to ensure polymer displacement effect. The consumption of fresh water in oil field has increased dramatically as the extension of polymer- displacement industrialization. Meanwhile extremely large amount of produced water has to be drained away, directly resulting in water resource waste and serious environmental pollution. To resolve this problem, LaMaDian Oil Field embarks on the study of using produced water in polymer-displacement process to realize recycle application of produced water.Lab tests show: microbes and reducing substances in produced water are major factors to influence polymer solution's viscosity. Although the TDS of produced water is relatively high (4000mg /L or so), the polymer solution mixed with it can still maintain a higher viscosity. At the same time, this kind of polymer solution has a desirable property to match the reservoir, and demonstrate a better ability to maintain its viscosity in simulative reservoir; a lot of tests prove that the method of exposure-to-oxygen is a economical and logical way to treat microbes and reducing substances existing in produced water; combining studies of viscoelasticity and displacement ability of polymer solution preparing in fresh water and produced water respectively with the latest mix and injection process, an injection method is determined finally that preparing super- high molecule weight polymer solution in fresh water and diluting it with produced water after exposure-to-oxygen treatment. Four fifth fresh water could be replaced with produced water by using this way. Good results have been achieved in field experiments conducted in 5# and 6# injection station, locating in west northern block of LaMaDian Oil Field.