Synthesis And Performance Of Water-soluble Polymer For Heavy Oil Viscosity Reduction

With the large and continuous consumption of conventional oil resources,the urgency of developing and utilizing heavy oil resources becomes increasingly prominent.Heavy oil is characterized by high viscosity,high density and poor mobility due to its high content of asphaltenes and resins,which leads to great difficulty in recovery and transportation and poor utilization rate of the resource.Therefore,how to reduce the viscosity of heavy oil and improve its fluidity become the key to break the barrier restricting its development and utilization.At present,the most common method for heavy oil viscosity reduction is to add water-soluble heavy oil viscosity reducers,among which polymer water-soluble heavy oil viscosity reducers have the most attractive performance in the application of oil fields.But the related research is still in the development stage,the reported polymers are few,their adaptability to heavy oil reservoir is limited,and the connection between solution properties and viscosity reduction mechanism is insufficient.The main trend of this field is to develop more new polymer water-soluble viscosity reducers that can better meet the needs of heavy oil reservoir and to deeply analyze the solution properties and viscosity reduction mechanism.Based on the above background,this dissertation focused on the design and synthesis of new water-soluble polymers as heavy oil viscosity reducers,their solution properties and heavy oil viscosity reduction performance.1.Hydrophobically associating water-soluble copolymers(AAG)with an epoxy group were first synthesized by free radical copolymerization of acrylamide and sodium 2-acrylamido-2-methylpropanesulfonic acid with glycidyl methacrylate.An amino-terminated amphiphilic copolymer(AS-N)was also prepared with acrylamide and sodium 4-styrenesulfonate.A series of water-soluble long branched-chain amphiphilic copolymers AAGASs were then obtained by the chain-extending reaction between the epoxy groups of the AAG and amino group of the AS-N.FT-IR spectra,1H NMR spectra,static light scattering(SLS),and TGA measurements of these copolymers were performed to determine the polymer structures and properties.Shear viscosity,surface tension and interfacial tension of these copolymers were also investigated to underst and the oil-displacement mechanism of AAGAS solutions.The results showed that AAGASs have a unique associative property in solution and possess good surface and interfacial activity,allowing AAGAS solutions to both thicken water and convert highly viscous heavy oil into low-viscosity oil-in-water(O/W)emulsions.The long chain structure plays an important role in the above properties.2.To provide an efficient and environmentally friendly candidate for heavy oil viscosity reduction under high-salinity conditions,a series of water soluble terpolymers(ANA)were synthesised through the solution copolymerization of acrylamide,N-vinyl pyrrolidone,and the synthetic cationic quaternary ammonium salt monomer N-(acrylamido propyl)-N,N-dimethyl,N-cetyl ammonium bromide(ADC).Basic characterization was carried out using FT-IR and H NMR spectra,elemental analyse,and static light scattering measurements.Solution properties based on the variation of surface tension and interfacial tension under different conditions were studied to optimise their use.The results showed that these terpolymers had moderate surface and interfacial activity for recyclable heavy viscosity reduction via emulsification and dehydration via demulsification,the introduction of the cationic monomer ADC imbued the terpolymers with a higher viscosity reduction rate with better mineral-tolerant heavy oil viscosity reduction ability.3.A novel amphiphilic terpolymer was synthesized with acrylamide,N,N-dimethyl acrylamide,and acryloyl morpholine,and a hydroxyl ended anionic copolymer was synthesized through chain transfer copolymerization of acrylamide and sodium styrene sulfonate,then a complex amphiphilic copolymer for heavy oil viscosity reduction could be obtained with two kinds of copolymers.The aggregation behaviour of these copolymers in aqueous solution was studied by resonance light scattering,and the changes of apparent viscosity,surface tension and interfacial tension with concentration were investigated.In addition,the viscosity reduction behaviour of heavy oil emulsification based on interfacial activity was studied by optical microscope and rotary viscometer,and the effects of different inorganic salts and salt concentrations on their heavy oil viscosity reduction performance were also analysed.The results showed that the complex synergism with a lower dosage to achieve a better salt-tolerant heavy oil emulsification viscosity reduction.4.A series of pH-responsive water-soluble polymers with different hydrophobic monomer contents was synthesized through the copolymerization of acrylamide,dimethylamino propyl methyacrylamide and perfluorohexyl ethyl methacrylate.The structures were characterized by NMR spectrum,FT-IR spectrum,static light scattering andthermogravimetric analyse.The solution properties of the copolymers were studied using interfacial dilatational rheology,viscosity and surface tension test.The influence of pH on the solution properties was investigated by Zeta potential test,and the pH-responsive heavy oil viscosity reduction behaviour was studied using laser particle size analyser and rotary viscometer.Results showed that the interfacial activity of these polymers increased with the fluoride monomer content increased and decreased with the solution pH decreased,based on the emulsification viscosity reduction mechanism controlled with interfacial activity,these polymers could emulsify heavy oil into O/W emulsion with high stability and achieve viscosity reduction when the pH is high,while realize rapid oil-water separation alter acidification.5.A series of CO2 responsive water-soluble polymers for heavy oil viscosity reduction were prepared by copolymerization of acrylamide,dimethylaminoethyl methacrylate and benzyl methacrylate.The apparent viscosity,surface tension,interfacial tension,and hydrodynamic radius of their solutions at different concentrations were studied.The reversible response to the CO2 switch was measured by conductivity meter.The heavy oil emulsification viscosity reduction performance was investigated by means of contact angle measurement,optical microscope observation and apparent viscosity measurement.These studies showed that the increase of hydrophobic benzyl methacrylate monomer content could enhance the hydrophobic association of the polymer,which benefits surface activity,interfacial activity,wettability and heavy oil emulsification viscosity reduction.The particle size of the formed O/W emulsion is positively correlated with interfacial tension and negatively correlated with continuous phase viscosity.The viscosity reduction behaviour of these polymers showed responsiveness of CO2.6.The heavy components of asphaltene and resin in heavy oil were separated and fully characterized by means of FT-IR spectra,NMR spectra,element analyse,UV spectra,GPC and TEM.On this basis,a water-soluble polymer for disassociating heavy oil viscosity reduction was synthesized and pilot-tested,the heavy oil viscosity reduction performance and mechanism were also analyzed.Study found that the asphaltene and resin present dense layered associating structure as they containing polycyclic aromatic structure and polar groups,our water-soluble polymer with large amounts of polar groups could destroy the associating structure of asphaltene and resin,therefore fundamentally reduce the viscosity of heavy oil.Proper shearing and aging treatment were beneficial to better viscosity reduction performance,the pilot product has great potential to be used in high temperature and high shear reservoirs.