SynopsisCopolymers of sodium acrylate and N-methyl-, N-isopropyl-, N-n-butyl-, and N-t-butylacrylamide were prepared. The viscosities of these copolymers in 0.01% and 2.00% NaCl and their resistances to shear were compared with those of several partially hydrolyzed polyacrylamides. The poly(N-alkylacrylamide-co-sodium acrylate demonstrated somewhat better retention of viscosity in brine than did analagous partially hydrolyzed polyacrylamides. N-alkyl substitution increased sensitivity to shear in low salt solutions.
INTRODUCTIONRising oil prices make tertiary oil recovery economically feasible. Efforts are underway in the United States and elsewhere to improve enhanced oil recovery (EOR) methods. Polymers play an important role in this process by thickening water in both surfactant/polymer and polymer flooding. Xanthan gum and partially hydrolyzed poly(acry1amide) (HPAM) have been used in these capacities. HPAM is the most widely used of these two polymer types despite characteristics such as viscosity loss in brines and shear stability. Two possible approaches for improving HPAM type polymers are (a) stiffening the polymer backbone and (b) substituting alkyl groups for one or both of the hydrogens on the amide nitrogen. The first approach is discussed in another paper by this gr0up.l The latter method (b) will be discussed in this paper.Hester et a1.2 have synthesized N, Ndimethyl and N, N-diethylacrylamide polymers for EOR evaluation, but surprisingly there is little work reported in the literature on the synthesis and testing of N-mono-substituted acrylamide polymers for this application. The present investigation consisted of the synthesis and evaluation of two homopolymers and four copolymers for possible use in EOR. The polymers studied were the following: (1) poly(Nmethylacrylamide), (2) poly(N-isopropylacrylamide), (3) poly(N-methylacrylamide-co-sodium acrylate), (4) poly(N-isopropylacrylamide-co-sodium acrylate), (5) poly(N-butylacrylamide-co-sodium acrylate), (6) poly(N-t-butylacrylamide-co-sodium acrylate).
EXPERIMENTALThe homopolymers and copolymers were prepared by aqueous solution polymerization, using potassium persulfate (KzS208)/sodium metabisulfite (NazS20,) as initiator/activator. Commercial monomers were purified either by distillation under reduced pressure or by recrystallization. The reactions were carried out in a nitrogen atmosphere, and the water used as the polymerization solvent was deaerated. Polymeric products were isolated and purified by reprecipitation and washing.Synthesis of Homopolymers. The experimental procedure followed to prepare these polymers was a very simple one. A weighed amount of monomer was dissolved in an appropriate amount of distilled, deaerated water in a 50-mL serum bottle. The bottle was flushed and sealed under a nitrogen stream. The initiator solution was then introduced into the bottle by syringe. At the appropriate stage, the reaction was terminated by pouring the viscous solution into a constantly stirred nonsolvent. When copolymers were made, the polyme...
SynopsisFive to six million molecular weight polyacrylamide and polymethacrylamides of comparable post-alkaline hydrolysis viscosities were imidized by dissolution and heating in 6N HC1. After alkaline hydrolysis, the imidized polymers demonstrated significantly better retention of viscosity to 2% NaCl than did similar partially hydrolyzed polymers. Viscosities in 0.01% NaCl and resistance to shear were not markedly affected by this modification. It is assumed that this improved performance in brine is the result of chain stiffening due to intrachain imide rings.
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