Qualification Rate Improvement Of Polymer-bearing Produced Water Treatment

Daqing Oilfield is now stepping into the third development stage which is characterized by the appearance of such problems as high water-cut phenomenon and produced water treatment caused by the chemical flooding. Due to the large-scale implementation of polymer flooding at Daqing, polymer has been detected in the produced water at most water treatment plants and its content tends to be rising at those specific polymer-bearing water treatment plants. To reduce the content of polymer in produced water, some high efficiency de-emulsifiers were tried and their dosage were also tested. The results show that the content of organics and suspended solids can be reduced by approaches including sedimentation plus air-floatation technique which is capable of removing most organics and suspended solids, and walnut shell filter to achieve further purification. Simultaneously, some water treatment chemicals called high efficiency flocculants were selected and added in the sedimentation tanks. To further improve the sedimentation tank efficiency, the continuous-oil–collection system was restored. Additionally, equipment called static perforated sledge discharge pipe was installed. Those measures result a decrease in the content of organics and suspended solids and an increase in water qualification rate, which potentially can be applied to the treatment and rejection of oilfield produced water. However, some problems may be met during the application, for instance, the stable state of produced water coalescence and separation is difficult to reach. To solve these problems, Daqing Oilfield Design Institute has implemented some field tests to evaluate the performance of oil-water separation agents at produced water treatment plants with a goal to achieve a stable state of coalescence and separation. The future study will focus on the feasibility and large-scale application of oil-water separation agents to treat oilfield produced water. Water filter using membrane separation technology will also be considered and tested.