Preparation Of Temperature-resistant And Salt-resistant Polyacrylamide Flooding Agent And Study On Carbon Dots Assisted Fluorescence Tracing

The development of petroleum resources involves complex physical and chemical processes.Most of the oil fields in my country use water injection development technology,but the recovery rate is limited.It is necessary to solve the heterogeneity through deep profile control and improve the injection fluid sweep coefficient.Although the tertiary oil recovery technology based on polymer flooding has achieved good results,it still has insufficient performance of oil displacement agent,difficult to break emulsion after emulsification of crude oil,insufficient stability,insufficient adaptability to oil reservoir,and high oil displacement cost.The problem requires in-depth study of the flood control agent that adapts to extreme conditions and its effect on enhanced oil recovery.Based on this,this thesis takes acrylamide(AM)as the main monomer and introduces different functional monomers 2-acrylamide-2-methylpropanesulfonic acid(AMPS)and sodium styrene sulfonate(SSS)respectively.The water-in-oil temperature-and salt-resistant microspheres were prepared by the polymerization of N,N’-methylenebisacrylamide(MBA).The influence of functional monomers on the performance of microspheres was analyzed by testing the performance of microspheres such as temperature resistance,salt resistance and interfacial tension.At the same time,fluorescent carbon dots were prepared and compounded with the microspheres to achieve the purpose of fluorescent marking and migration tracing of the displacing agent,and the oil displacement performance of the microspheres was studied through an indoor sand-filled tube experiment.The details are as follows:(1)By reverse phase emulsion polymerization method,AM is the main monomer,and AMPS is the functional monomer,salt-resistant P(AM-MBA-AMPS)microspheres are prepared under the redox initiation system,and the single factor experiment is used to optimize polypropylene The best preparation process of amide microspheres is:emulsifier(Span-80/Tween-80)ratio is 17:3,oil-water ratio is 13:7,monomer content is 20 wt%,monomer ratio(AM:AMPS)is 8:1,the amount of crosslinking agent is 2.9 wt%,the amount of initiator is 0.06 wt%,the initial reaction temperature is 40℃,the stirring rate is 400 r/min,and the pH is 7.Fourier infrared spectroscopy(FT-IR),transmission electron microscopy(TEM)and scanning electron microscopy(SEM),and nano particle size analyzer(DLS)were used to characterize the structure and morphology of the microspheres,respectively.The results show that the particle size of P(AM-MBA-AMPS)microspheres is 328 nm,which is a spherical structure with regular morphology.Performance testing shows that it has good thermal stability,the highest water absorption rate reaches 5.9 times,and has strong salt resistance;the interface activity is less affected by temperature and salinity.(2)Using the best preparation process of P(AM-MBA-AMPS),replacing functional monomers from AMPS to SSS to prepare temperature-and salt-resistant P(AM-MBA-SSS)microspheres by inverse polymerization.The test results show that the particle size of the microspheres is 460 nim,the viscosity is 32 mPa·s,and the morphology is more regular.It has better stability and heat resistance.The thermal decomposition within 300℃ is only 5%,and the water absorption rate is up to 4.3 times.P(AM-MBA-SSS)has a more powerful ability to reduce the interfacial tension of oil and water.The adaptability of the reservoir is higher.(3)Using triammonium citrate as a carbon source to prepare fluorescent carbon dots(CDs)by microwave method,using FT-IR,TEM,DLS and fluorescence spectrometer and X-ray diffractometer(XRD)to measure the structure of carbon dots,Characterize the morphology and fluorescence performance;emulsify the carbon dots and P(AM-MBA-SSS)microspheres with excellent performance to form a fluorescent composite emulsion,obtain the most stable composite emulsion preparation process,and test the morphology of the composite emulsion by TEM.The results show that the carbon dot is a spherical-like structure with a particle size concentrated at 3-7 nm,and its life span is about 10.95 ns at the maximum,the quantum conversion rate is 23%,it emits blue light under ultraviolet irradiation,and has excellent dispersion in water.Can effectively reduce the interfacial tension.The average particle size of the fluorescent composite emulsion is 955 nm.TEM confirmed that the structure of the composite emulsion is water-in-oil-in-water type,which has higher stability.The fluorescence of the composite emulsion is more obvious.(4)Through the indoor simulated core flow experiment,the application performance of the three microspheres was investigated.The experimental results show that P(AM-MBA-SSS)has the best yield increase effect,and the recovery factor is increased by about 15%.P(AM-MBA-AMPS)microballoons increase production by about 9%after CDs drive.CDs/P(AM-MBA-SSS)increased output by about 7%,and after irradiating the produced liquid with ultraviolet light,obvious fluorescence appeared,proving that carbon dots can be used in combination with microspheres,fluorescent marking and migration tracking of microspheres,with on-site large The potential for large-scale applications.