Synthesis And Properties Of High Temperature-resistant Polyacrylamides

With the application of polyacrylamide (PAM) expanding to reservoir with hightemperature in the expect of fracturing, temporary plugging and profile controlling forEOR, improving its thermal-resistant, salt-tolerant and shear-resistant properties hasbeen a pressing research topic recently. Changing the structure of copolymers bycopolymerizing with hydrophobic monomers and adding stabilizers to the solution ofpolymer are two major means.In order to obtain the suitable composition of polymer and formula that can beused under high temperature conditions, the effect of different stabilizers upon thestability of PAM under aerobic conditions at high temperature has been studied in thisarticle through measurement of viscosity changes of PAM aqueous solution instainless steel tanks at150℃. A series of modified polyacrylamide copolymers suchas P(AM-AMPS), P(AM-AN), P(AM-NVP) and P(AM-AN-NVP) have beenprepared with AN, NVP and AMPS as functional monomers. The hydrolysis kineticsof these polymers and the effects of temperature, pH value on hydrolytic process havebeen researched. Meanwhile, in this paper hydrophobically associatingpolyacrylamide copolymers of AA, AM and QDMAC12or QDMAC16were preparedwith water as solvent, and QDMAC12or QDMAC16were prepared throughquaterisation of1-bromododecane or1-bromohexadecane withN-(3-dimethylaminopropyl)-methyl-acrylamide. The effect of the structure andcontent of hydrophobic monomer on critical aggregate concentration (CMC) andsolubility of hydrophobically associating polymers have been discussed.The experiment result shows that the reducing sodium sulfite and sodium sulfidehave good oxygen removal effect. PAM aqueous solution with saturated dissolvedoxygen can stay stable more than20days at150℃in the presense of2000ppmsulfite and sodium sulfide. The thermal-resistant performance of PAM aqueoussolution can be improved further through adding sacrifice agents formaldehyde,thiourea, N,N-dimethyl-formamide and dimethyl-propanediamine to aqueous solution.The rate of hydrolysis and ultimate hydrolyzed degree of copolymers are reduced bycopolymerizing AM with AN. Adding a certain concentration of AN to NVP-AMpolymerization system could increase the mass fraction of NVP in the copolymer andimprove the hydrolysis resistance of PAM copolymers notably. Hydrophobically associating polymers could be synthesized throughpolymerization of hydrophobic monomers QDMAC12and QDMAC16with AM, AA inhomogeneous aqueous solution. The hydrophobically associating polyacrylamideexhibit excellent solubility if the concentration of hydrophobic monomer inpolymerization system is lower than the CMC, on the contrary, the hydrophobicallyassociating polyacrylamide copolymers is difficult to dissolve and the solubility ofcopolymers could not be improved by adding surfactant to polymerization system.Along with the increase of hydrophobic monomers content, the CMC ofhydrophobically associating copolymers decreases,and the optimal content ofDMAC12in copolymer chain is2.5%，in such condition the CMC of copolymer is2700ppm.