Study On Reversed-phase Emulsion Polymerization Of Hydrophobically Associating Polyacrylamide And Its Performance

It is mainly typified that surfactant flooding,polymer flooding,alkali flooding and binary flooding in EOR technology at present,and among which the polymer flooding has obviously attracted attention both at home and abroad due to its enhanced oil recovery.Hydrophobically associating polyacrylamide has intermolecular association due to the intertwining between hydrophobic groups,forming a spatial network structure,and compared with ordinary polyacrylamide,it has good thickening performance.It has important application prospects in the field of petroleum extraction.The surfactant has good emulsifying,dispersing and stabilizing effects on the hydrophobic association water-in-oil emulsion,and it has good function of decreasing interfacial tension.Therefore,in this paper,a good performance of surfactant combination system was screened out for the preparation of hydrophobic associative polymer emulsion and studied the synthesis and properties of amphoteric hydrophobically associating and cationic hydrophobically associating polyacrylamides.(1)By compounding the lipophilic surfactant sorbitan fatty acid ester(Span80)respectively with hydrophilic surfactants polyoxyethylene sorbitol fatty acid(Tween-80),octaphenylpolyoxyethyiene(OP-10)and alkanolamide(AMD),an excellent compound surfactant system WY(Span80/AMD)was screened out with m(Span80):m(AMD)=2:1.The interfacial tension of surfactants AMD and WY were respectively determined,and the emulsifying properties of WY were evaluated.The results showed that the WY system could effectively reduce the oil-water interfacial tension and has good oil displacement;The WY solution had good emulsifying ability to oil and could be used as emulsifier in the process of reverse phase emulsion polymerization.(2)The amphoteric hydrophobic associated polyacrylamide thickener(AP-AM18)was synthesized by using acrylamide(AM),2-acrylamide-2-methyl propane sulfonic acid(AMPS)and a hydrophobic long chain alkyl allyl ammonium chloride(RM18)as the monomers through inverse emulsion polymerization.The optimum synthetic conditions were:emulsifier accounts for oil volume fraction 12.5%,monomer total mass fraction 25%,pH=6~7,reaction temperature 30?,reaction time 6h.The molecular weight of the AP-AM18 was determined to be 3.1×10~6 by waters gel chromatography(GPC).The structure of AP-AM18 was characterized by infrared spectroscopy(FT-IR),nuclear magnetic resonance spectroscopy(~1HNMR)and X-ray diffraction(XRD),and the performance of AP-AM18 solution was tested by dynamic laser light scattering particle size analyzer,thermo gravimetric analyzer(TGA)and dynamic rheometer.The results showed that the polymer AP-AM18 had an amorphous structure;The emulsion had an average particle size of about 100nm and concentrated distribution,emulsion stability;the quality of AP-AM18 was basically unchanged after the decomposition temperature exceeded 500?,with good temperature resistance;When the concentration was 2%,the apparent viscosity of the AP-AM18 reached 893mPa·s in the clean water and the apparent viscosity of the AP-AM18 reached 391 mPa·s in 5×10~4 mg/L mineralized water,indicating that it had good thickening and salt resistance performance;AP-AM18 soluion was pseudoplastic fluid and the apparent viscosity could still reach 93mPa·s after shearing for 200s,showing a strong shear resistance;Storage modulus G'and loss modulus G"with the change of stress was basically unchanged,G'>G",and had a strong viscoelastic properties and anti-strain ability.(3)A cationic polyacrylamide emulsion PAM1 was prepared by using AM and 2-methyl-acryloyloxyethyl-trimethyl ammonium chloride(DMC)as the monomers through inverse emulsion polymerization.The optimum synthetic conditions determined were that w(initiator)=0.08%(based on the total monomers),w(monomer)=22%,reaction temperature was at 35?and reaction time lasted for 6h.The molecular weight of the polymer PAM1 was determined to be 8.2×10~5 by GPC;The structure and properties of the emulsion PAM1 were characterized by means of FT-IR,dynamic laser light scattering particle size analyzer and dynamic rheometer.The results showed that the particle size distribution of PAM1 emulsion was narrow and the emulsion was stable;PAM1solution was pseudoplastic fluid.After shearing 200s,the apparent viscosity decreased from 277mPa·s to 253mPa·s,showing good shear resistance.(4)DMC instead of AMPS,by adding a functional hydrophobic long-chain RM18 and AM,an emulsion type hydrophobic associating cationic polyacrylamide(HAM-D)was synthesized through inverse emulsion polymerization.The optimum synthetic conditions determined were that m(oil):m(water)=1.25,w(initiator)=0.04%(based on the total monomers),w(monomer)=24%,reaction temperature was at 35?,reaction time lasted for6h.The molecular weight of the polymer HAM-D was determined to be 2.8×10~6by GPC;The structure and properties of the prepared HAM-D were characterized by means of FT-IR,~1HNMR,XRD,dynamic laser light scattering particle size analyzer,TGA and dynamic rheometer.The results showed that HAM-D had narrow distribution of emulsion particle size and good emulsion stability;Compared with PAM1,HAM-D had good heat resistance;The apparent viscosity of the HAM-D aqueous could reach 163mPa·s in 5×10~4mg/L mineralized water,reflecting that it had good thickening and salt resistance performance.After shearing 300s,the apparent viscosity decreased from249mPa·s to 236mPa·s,showing an excellent shear resistance.The storage modulus G'and loss modulus G"along with the increasement of stress decreased basically unchanged,G'>G",and showed that HAM-D had strong viscoelasticity.