Evaluation of Operating Effect of Pretreatment Process of Oilfield Heavy Oil Produced Water Reused in Boiler
The composition of the produced water of heavy oil in oilfields is complex,with high sa-linity and high concentration of silica.Heavy oil produced water is treated by conventional heavy oil sewage treatment process,and reused in the boiler,which causes scaling inside the boiler,and affects the safety production and steam quality of the boiler.In order to solve the scaling problem of oilfield steam injection boiler,the technology of deep silicon removal and salt reduction of sewage is adopted.However,the water supply requirement of reverse osmosis membranes is relatively strict,purified and softened heavy oil sewage entering the reverse osmosis membrane can easily cause fouling and blockage of the membrane,and the effect of salt removal is unstable.The influencing factors of scale formation in reverse osmosis membranes are analyzed as organic matter,silica,and aluminum ions in water.Based on the conventional heavy oil sewage treatment process,sewage coagulation and silicon removal,mi-cro-flocculant filtration,and ultrafiltration are added.The COD is reduced from 419.8 mg/L to 201.5 mg/L,the mass concentration of silica is reduced from 333.9 mg/L to 39.6 mg/L,the mass concentra-tion of aluminum ions is reduced from 0.268 mg/L to 0.032 mg/L.The feed water SDI of the reverse osmosis membrane is less than 5,the turbidity is less than 1NTU,and the conductivity of the reverse osmosis membrane produced water is less than 2000 μs/cm.The water quality of the steam injection boiler is improved,the steam quality of the boiler is improved,and the problem of silica scale and salt scale in the oilfield steam injection boiler is solved.
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