Study On Synthesis Of Water-Soluble Copolymers And Their Viscosity Reduction Properties To Heavy Oil

Heavy oil refers to high-viscosity heavy crude oil with a viscosity greater than 50 mPa·s under formation conditions,or with a viscosity of 1000?10000 mPa·s of a degassed crude oil at the oil layer temperature.Due to high viscosity and poor fluidity,heavy oil is difficult to be effectively exploited under conventional technical operations.Now that the industrialization is developing so rapidly,the demand for petroleum resources is increasing.Therefore,how to take more effective measures to extract heavy oil is particularly important.In the process of viscosity reduction of heavy oil,the amount of surfactant viscosity reducer is large,and the emulsion formed is stable,so it is necessary to demulsify in the next operation,thus increasing the operation cost and economic cost.Therefore,choosing cheap,high-quality and efficient viscosity reducer is the key to viscosity reduction.A good viscosity reducer should meet two aspects:Firstly,it has a certain surface activity to effectively reduce the viscosity of heavy oil;secondly,the formed oil-in-water emulsion can't be stabilized for too long,otherwise the post-treatment operation cost will be increased.At present,the main method to solve this problem is to add water-soluble viscosity reducer with low surface activity to reduce viscosity.However,there are few reports about polymer water-soluble viscosity reducers for heavy oil at present,and the synthesis of viscosity reducers and the mechanism of viscosity reduction are not mature.Under this background,several water-soluble viscosity reducers for heavy oil were designed and synthesized in this paper,which were mainly discussed from three aspects:structural characterization,functional application and viscosity reduction mechanism.(1)The terpolymers with low interfacial activity were prepared by radical copolymerization of acryloyl morpholine,sodium maleate and N,N-dimethylacrylamide.The structure of the copolymer was characterized by 1H NMR spectra,FI-IR spectra and elemental analyses.The solution properties of copolymer were studied by surface tension and interfacial tension test,and the dehydration degree of oil-water emulsion was explored by stability analyzer.The viscosity reduction mechanism of terpolymer on heavy oil was studied by rotational viscometer,cyclic viscosity reduction performance test,contact angle test,scanning electron microscope and transmission electron microscope.The results show that the copolymer has low surface interfacial activity due to the hydrophilic property of maleate,and the oil-water separation is faster under this condition.Acryloyl morpholine(ACMO)and N,N-dimethylacrylamide(DMA)destroy the hydrogen bond and ?-? stacking structure of asphaltene and resin in heavy oil,thus fundamentally reducing the viscosity of heavy oil and enhancing its flow performance.(2)The preparation of copolymers was conducted by the free radical copolymerization of vinyl pyrrolidone and sodium maleate.The 1H NMR spectra and FI-IR spectra were conducted to analyze the structure of the copolymer.The dynamic light scattering was used to investigate the aggregation behavior of copolymer solutions.The surface activity and interfacial activity of copolymers under different conditions were determined by surface tension and interfacial tension test.The cyclic performance of copolymer and asphaltene dispersion in heavy oil were studied by rotational viscometer and transmission electron microscope test.The result shows that the moderate surface activity is beneficial to the stability of oil-water emulsions.With the increasing of cyclic viscosity reduction tests,the viscosity reduction effect of copolymers on heavy oil gradually weakens.(3)Poly(vinyl pyrrolidone/maleate)was modified by amines with different alkyl chain lengths to obtain copolymers.The 1H NMR spectra and FI-IR spectra were conducted to analyze the structure of the copolymer.The surface activity and interfacial activity of copolymers were studied by measuring the surface tension and interfacial tension in pure water and mineralized water,respectively.The viscosity reduction performance of copolymers in pure water and mineralized water was tested and analyzed by rotational viscometer.The stability time of oil-water emulsion was investigated by stability analyzer,and the structural changes of resin and asphaltene before and after viscosity reduction were analyzed by FT-IR spectra.The results showed that the interfacial activity of the copolymer was improved due to the action of inorganic salts,and the copolymer had good salt resistance in the process of viscosity reduction.In mineralized aqueous solution,when the concentration was 1.5 mg/mL,the viscosity reduction rate could still reach above 91.3%.As the length of the alkyl chain increasing,the stability of the emulsion formed by the copolymer solution and the heavy oil is better and the stability time is longer.