Pollution Mechanism And Plugging Removal Technology Of Polymer Flooding Sewage Recycle Wells In Xingnan Oilfield

With the long-term polymer flooding waste water recycle,polymer combined with various reservoir materials,resulting in pollution and blockage,resulting in a decline in oil recovery.Therefore,Xing-nan Oilfield carried out acidifying blockage removal measures and achieved good experimental results,but since 2014,the acidifying blockage removal effect of Xingnan Oilfield has been declining year by year,seriously affecting the oilfield development effect.It is found that the simplicity of acidifying plugging removal formula leads to poor plugging removal effect of polymer-containing sewage recycle wells and can not meet the needs of oilfield production.Therefore,it is an urgent problem to develop a set of recipe suitable for sewage recycle and plugging removal in Xing-nan Oilfield.In this paper,the composition of backwater and oil scale in polymer-containing sewage recycle wells in Xing-nan Oilfield is determined by chemical analysis.The main pollution mechanism is polymer plugging,oil scale plugging and inorganic scale plugging.According to different plugging mechanism,different plugging removal process design and core injection parameters optimization are formulated.The results show that:(1)The polymer plugging removal formula has been developed.The polymer degradation rate can reach 99.91% and the bacteria in the vomiting waste-water can be well inhibited.Combining with the core simulation polymer plugging experiment,the polymer plugging removal agent has remarkable plugging removal effect for injecting different concentration polymer.The permeability recovery rate of core can reach 95.01% at the polymer concentration of 3500 mg/L.(2)In view of scale blockage,an oil scale inhibitor has been developed.The scale inhibition rate of the formulation can reach 81.5% or more(0.5% of the scale content).The polarizing microscope observation shows that the formulation can effectively inhibit the deposition of oil scale.(3)Aiming at the blockage of inorganic scale,a non-acid solution blockage removal technology has been developed.The highest dissolution rate of calcium carbonate can reach75.6%.The formula has the advantages of strong inhibition,low corrosion,pollution-free and easy to transport safely.(4)The injection parameters of plugging removal agent were optimized through laboratory experiments of plugging polymer-containing waste-water.The optimum injection rate was 0.3m L/min,the optimum injection volume was 1PV,and the optimum injectionsequence of plugging removal agent was as follows: oil scale inhibitor,polymer plugging removal agent and inorganic scale plugging removal agent.The permeability recovery rate of the formula for simulated plugging core was 92.8%,and the effect was remarkable.