Study On Rule And Control Technology Of Viscosity Loss Of Oilfield Produced Water For Preparing Polymer Solution

Polymer flooding of EOR is widely used in oilfield at domestic and abroad now, with the continual enlarging of production scale of polymer flooding industrilization, the provision of low-salinity water increases, and the disadvantage of depending on the low-salinity water to configure and dilute polymer solution stands out. Especially during the super-high watercut period, the produced water increases, this method not only waste water resource, but also result in the emission of sewage and seriously pollute the environment. At present, Daqing Oilfield has already carried out the process of polymer solution diluted by the sewage. Although the test acquired partly effect, due to the water quality difference between the sewage and low-salinity water, the viscosity of polymer solution diluted by the unsettled sewage has the lower viscosity than the same concentration of polymer solution diluted by low-salinity water and inferior displacement efficiency, for example in No.3 Oil Factory of Daqing Oilfield.To utilize the sewage in polymer flooding, the method of improving the viscosity of polymer solution diluted by sewage is studied.This paper analyzed the water quality of the sewage of different treatment depths and the influence on the viscosity, researched the factors affecting the polymer solution viscosity such as salinity, reducing substances, bacteria, oil, suspended solids and residual polymer. It was found that the sewage was characteristiced by high content of salinity and reducing substances, the number of microorganisms was also high.Therefore the aeration simulation experiments were carried out considering the microorganisms and reducing substances. The results showed that the reasonable concentration level of produced water aerobic concentration was between 6mg/L and 8mg/L, the viscosity of polymer solution prepared with different molecular weight and different concentrations could be increased more than 4mPa.s by effectively killing or reducing the bacteria or reducing substances, and the viscosity of polymer solution prepared with the sewage treated by aeration and sterilization technology could be futher increased by 10~15% on the basis of field technology. The recycling use of treated sewage would contribute to reducing the cost of polymer injecting, enhancing the development and protecting the environment.