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N,N-dimethylacrylamide (DMAA), 2-acrylamido-2-methyl-1-propyl (AMPS), dimethyl diallyl ammonium chloride (DMDAAC) and N-vinylpyrrolidone (NVP) monomers were copolymerized to synthesize a zwitterionic copolymer filtrate reducer. The results of Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) indicated that the molecular structure and chemical compositions of the quadripolymer matched with the design, and the result of the differential scanning calorimetry (DSC)-thermogravimetric analysis (TGA) showed that the polymer had good thermal stability. The effects of the quadripolymer on the properties and salt tolerance of drilling fluids were investigated. The environmental scanning electron microscope (ESEM) was used to observe the microstructure of the DMAA/AMPS/DMDAAC/NVP quadripolymer-bentonite system and filter cake of the drilling fluid added the copolymer. Results showed that a one space grid structure was formed by the molecular film with a hydrophobic association effect and electrostatic interaction between the groups in the positive and negative charges of the quadripolymer. It adsorbed and coated clay particles, and kept the particles distributing multilevels which contributed to forming a compact filter cake to reduce fluid loss. The spatial structure of the quadripolymer in drilling fluid could be destroyed partly by high temperatures, sodium and calcium, but the polymer still had a good effect on reducing fluid filtration.

journal of polymer engineering

Synthesis and properties of high temperature resistant and salt tolerant filtrate reducer N,N-dimethylacrylamide 2-acrylamido-2-methyl-1-propyl dimethyl diallyl ammonium chloride N-vinylpyrrolidone quadripolymer