| After long-term development,most of China's oil fields have entered the middle and later stages of mining,and the water content of crude oil has also increased year by year.It has entered the late development stage of“three highs,”high water content,high production viscosity,and high oil production rate.In order to further increase the development scale of water flooding,tapping and tertiary oil recovery,Daqing oilfield further increased the amount of water and water in the oil field,and in order to increase the oil displacement effect,large-area ultra-high molecular weight and high concentration polymer injection technologies were adopted.The polyacrylamide flooding has received great attention due to its high oil production.At present,Daqing oilfield has become the world's largest oil recovery technology using polymer flooding technology.However,polyacrylamide will increase the viscosity of the produced water,resulting in a decrease in the natural sedimentation performance of the suspended solids.The emulsified degree of the crude oil in the produced water will increase,and the difficulty in separation of oil and water will increase.The water quality after treatment will be seriously exceeded.In this paper,based on the characteristics of the quality of produced water in Daqing Oilfield,the surface appearance,microscopic appearance and organic composition of the polymer in raw water were analyzed through laboratory experiments.It is known that the polymer produced in Daqing Oilfield is not a single polyacrylamide.,but the polyacrylamide and the surface active agent of the petroleum sulfonate reagent crosslinked to form a binary copolymer;the current high polymer is the main cause of water quality failure of the sewage treatment system,the components of the composition of COD in the sewage The polymer contribution reaches 75%.Due to the chelating reaction between the metal ions such as calcium and magnesium and the polymer,and the strong hydration of the sulfonic acid itself,the polymer is highly stable in the sewage,and the conventional dosing,flocculation,separation,etc.It is difficult to destabilize and remove highly stable polymers in wastewater.The research explored and screened feasible processes from technologies such as physics,chemistry,biochemistry,filtration,adsorption,etc.,and effectively removed and degraded the high-polymers in the sewage in advance to meet the following biochemical treatment conditions,thereby achieving the purpose of reducing COD.The test proved that the use of small molecules,high activity,strong oxidizing substances to break or weaken the hydration layer,and then compress the double layer,and by adding a high-molecular organic filter aid to destroy the stability of the entire structure,adding flocculant so that A large number of destabilized polyacrylamides and surfactants are settled and removed by physical methods to improve the biodegradability of sewage and meet emission standards,which is the key to technology selection.The process technology route of “electrocatalytic gas flotation-including coagulation and sedimentation-enhanced MBBR biological treatment-filtration”was finally selected.The process was proven to be stable and reliable in the on-site pilot test,and the catalytic effluent average effluent polymer content was 43 mg/L,COD=131mg/L.After the pilot test operation,the overall process final treatment of water COD?100mg/L.It is hoped that this research project can be used as a reference for the research on the treatment technology of high-concentration oil production wastewater in Daqing Oilfield. |
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