Industrial Experimental Study On Combined Flooding Of Sewage In Xinjiang Oilfield

At present,chemical flooding projects in Xinjiang oil fields mainly use fresh water.With the deepening of the concept of green environmental protection,sewage compound flooding prepared with sewage will gradually occupy a dominant position.Compared with clean water,sewage contains a large amount of bacteria,inorganic salts,and organic impurities,which have a huge impact on polymer viscosity;at the same time,it will also play a significant role in reducing the interfacial tension of composite flooding.Therefore,it is of great practical significance to study the effect of sewage system on the viscosity,interfacial tension and flooding efficiency of composite flooding and to use the treated sewage to formulate compound flooding fluid,regardless of economic interests or environmental protection.This paper analyzes the water quality of the inbound and outbound waters of the No.81 sewage treatment station in Xinjiang Oilfield,and finds out the factors that may affect the polymer viscosity,such as cations(Na⁺,Ca²⁺,Mg²⁺),Fe²⁺,S^2-,and other inorganic anions.The effect of each influencing factor on polymer viscosity was determined by four factors and three levels of orthogonal experiment to determine the main influencing factors and secondary influencing factors.Through long-term stability experiments,the effects of various major influencing factors(Ca²⁺,Mg²⁺,Fe²⁺,S^2-)on the long-term stability of polymer solutions were investigated.At the same time,the effects of different water treatment agents?flocculants,demulsifiers?and other factors?oil content,temperature,pH,suspended solids?on the viscosity of the polymer were studied.By comparing the interfacial tension effects of different oil samples in the mixed KPS under clean water conditions,the ideal experimental oil sample and the compound surfactant were selected.By comparing the effect of sewage at different water treatment stages on the interfacial tension of the ternary system,it is found that under the same experimental conditions,the inbound water of the No.81 station is better than the outbound water of the No.81 station,and the system has universal applicability in different oil samples.By comparing the interfacial tension,the viscosity and the Zeta potential between the inbound water of the No.81 station and the chean water,it was found that the combined water flooding of the No.81 station is not only more effective,but also has a better range of adaptability.In the range of alkali concentration and surfactant concentration,and at different oil-water volume ratios,the absolute value of Zeta potential at the oil-water interface of the ternary emulsion system at inlet of station No.81 must be greater than that of the corresponding clean water system,and the stability of the emulsion are better than the ternary system formulated with clear water.Compared with the clean water system,the ternary system of the station No.81 station has a certain viscosity loss.However,the lost viscosity is in an acceptable range compared to the benefits of the inlet water at the No.81 station in terms of interfacial tension and emulsion stability.