Abstract:

With the continuous promotion of chemical flooding in Xinjiang Oilfield,the demand for water for liquid distribu-tion is increasing.In order to meet the requirement of environmental protection,it is an inevitable choice to use oilfield sewage to prepare chemical flooding solution instead of fresh water.However,there are sulfate reducing bacteria and other interfering substances in oilfield wastewater,which have great influence on viscosity retention and interfacial tension of chemical flood-ing system.By analyzing the composition of dilute oil wastewater from No.72 station,the effect of different alkalis on viscosity retention,interfacial tension and displacement efficiency of the chemical flooding system with wastewater mixture were inves-tigated.The results showed that NaOH could inhibit sulfate reducing bacteria and improve the viscosity retention rate of che-mical flooding system,but the interfacial tension could reach 10^-3 mN/m only when the mass concentration was above 1%;Na₂CO₃ could also inhibit sulfate reducing bacteria and enhance the viscosity retention rate of the system,but the effect was worse than NaOH;The interfacial tension of the system could reach 10^-3 mN/m when the mass concentration was above 0.2%;NaHCO₃ could not inhibit SRB,so the viscosity retention rate of the system was the lowest,and its interfacial tension could only reach 10^-1 mN/m.The results of oil displacement showed that the NaOH wastewater system could only reduce the water content to 67% and maintain low water content for a short time at the stage of chemical agent injection,the Na₂CO₃ wastewater system could reduce the water content to 64% and maintain low water content for a long time.

Key words: oil wastewater, chemical flooding solution preparation, viscosity retention, alkali, adaptability