Numerical Simulation On The Graded Media Filtration Process Optimization For Polymer-Flooding Produced Water

Along with the exploitation of the oil fields and the spread of oil development methods after high water cut period,the produced water not only increases significantly in scale,but also becomes more complex in water quality characteristics.For example,polymer-flooding produced water(PFPW)shows the typical qualities such as the increases of water viscosity,amount of reducing substances and emulsified oil,and the decreases of oil-water interfacial tension,and oil particle size.So a series of problems such as the longer gravity sedimentation time,the shorter backwashing cycle,the worse ability of containing the pollutants and the more sludge deposition are presented during the treatment.The optimization of treatment process for PFPW is facing many requirements and challenges,especially for the thin and poor reservoir which needs the higher requirement of water quality.Therefore,for the pressure filtration unit after gravity sedimentation,the influence of the filling mode of graded filter media in filters and quality characteristics in PFPW on the flow field and filtration effect was investigated in the study basing on the optimization of filter water distribution process by numerical simulation,according to test and analysis of water quality characteristics.And the pressure filtration process for PFPW was optimized,which can provide effective support for realizing the improvement of PFPW treating or converting to the potential water source.The results show that the good performance of water distribution is obtained and the pressure drop in the filter with sieve tubes is reduced by 30.56% under different treating capacities compared with the filter with slots.And the filter of 4 meter diameter with nine sieve tubes is optimized by its excellent water distribution characteristic.With the increase of the polymer concentration,the pressure drop of filtration flow field increase,the distribution uniformity of oil and suspended particles is weakened,and following by the bad the pollution load performance of filter media.However,the stable filtration flow field and the good filtration performance is showed when using the graded filter media instead the uniform media.The results show that the removal rate of oil and suspended particles in double-layer graded filter media increase by 15.58% and 18.08% compared with uniform filter media when the concentration of polymer increases to 820 mg/L.Furthermore,a two-stage filtration deep filtration process is proposed for the PFPW after ordinary treatment to reduce the concentration of the oil and suspended particles below 5 mg/L.And the two-stage filtrationprocess of “double-layer graded filter media + three-layer graded filter media” is optimized and presented by the numerical simulation,and the results also show that the removal rate of oil and suspended particles can reach to 87.78% and 87.11%,respectively,which is a potential and promising treatment process for the PFPW after ordinary treatment.