Synthesis And Properties Of Polyacrylamide Copolymer Microspheres

Profile control and water shutoff technologies have always been one of the most effective methods of improving water injection exploitation in oilfield and realizing the stimulation of oil reservation. For water shutoff profile, special emphasis has been concentrated on deep flooding technology. Polymer microspheres, a class of water-absorbing resins mainly consisted of polyacrylamide(PAM) materials, have been extensively used in many fields. The amides-based groups on the surface of these polymer microspheres could swell and gelatinize under certain circumstances, which could form effective blocks in the gaps and pore throats, thus improving oil recovery. Therefore, in this thesis, core-shell microspheres with big particle size were prepared by dispersion polymerization, and the optimization of process conditions was carried out. Moreover, the relationship between the structure and properties of PAM microspheres as well as the actual flooding effects of the microspheres was also investigated.Firstly, by optimizing the experimental conditions and steps, the optimal preparation process of PAM copolymer microspheres was explored. A one-pot and two-step polymerization method was developed: at the first step, the core part of core-shell PAM copolymer microsphere was synthesized; then, the shell part was prepared on the surface of core part by further addition of experimental reagents under the same conditions. Meanwhile, one-factor experiments were designed to investigate the influence of different reaction conditions, including the concentration of monomer, initiator, crosslinker, dispersant, stirring speed, and temperature, on the results of PAM copolymer microsphere size and monomer conversion ratio.Secondly, transmission electron microscope(TEM), fourier transform infrared spectrometer(FT-IR), optical microscope and laser particle sizer were used to characterize the structure, composition, morphology, particle size, as well as the expansion properties of the samples and their stability in water. The results showed that PAM microspheres possessed an obvious core-shell structure and a uniform particle size distribution in the range of 10~30?m. Furthermore, the effective control of the microspheres diameter as well as the size ratio of core part and shell part could be achieved by changing the feed ratio of core part reagants and shell part reagents. At 60?, the size of PAM microspheres could expand by as much as 20~50 times with increasing of water-absorbing time, thus forming effective block in the gaps and pore throats.Finally, the effects of PAM microspheres on the actual flooding performance in high-permeability zones of oil reservoir were evaluated by indoor simulation experiment, in which all the experimental conditions were the same as the underground conditions. The results showed that the obtained PAM copolymer microspheres exhibited excellent plugging ability and the plugging ratio could be over 98%.