Effect Of Degree Of Hydrolysis On Salt Resistance Of Amphoteric Polymers

Polymer flooding is considered as one of the most important technologies for enhanced oil recovery (EOR) in our country and the polyacrylamide polymer is widely used among the water-soluble polymers. But they were hydrolyzed under high temperature conditions, resulting in poor stability of the polymer solution. However, the zwitterionic polymer has good salt tolerance due to its unique structure "anti-polyelectrolyte effect", but the hydrolysis still can’t stop. So the performance of hydrolyzed zwitterionic polymer has become an important factor to affect and limit the use of this new polymer in reservoirs. Therefore, studying the influence of hydrolysis degree on properties of zwitterionic polymcrs solution has a great practical value and will give some reference and guidance to field application and synthesis of such polymers.Firstly, this dissertation synthesized and characterized the zwitterionic polymer PCBA which its monomers made in laboratory, PADA and polyacrylamide PAM under the same conditions. Then, in the optimum hydrolysis conditions respectively hydrolyzed to higher hydrolysis degrees of HPCBA, HPADA and HPAM. Lastly, the relationship between the macro-regularities of the different hydrolysis degrees of HPCBA, HPADA and HPAM solutions and the solution microstructure is studied by the methods of viscosity, visco-elastic and light scattering. Tthe results show that:In distilled water, the viscosity of different hydrolysis degrees solutions of HPCBA, HPADA and HPAM showed an upward trend with the increase of polymer concentration and a downward trend with the increase of temperature. Moreover, with the increase of hydrolysis degree, their apparent viscosity, storage modulus G’ and loss modulus G" increased first and then decreased. And in the studies of anti-temperature and anti-aging stability, the performance of HPADA is superior to HPCBA and HPAM.In salt water, the effect of metal cations on polymer solution followed by Mg2T, Ca2+, and Na+. To HPAM, its viscosity plummeted with the metal cations, while the HPCBA and HPADA solution showed a decline first then slowly rising. The salt tolerance of HPCBA is better than HPADA and HPADA is better than HPAM. In the studies of rheological, the added salt improved the polymer solution’ shear resistance over a range of shear rates. In the suitable region of oscillation frequency, the polymer solution was gradually changed from the viscous-fluid to elastic-fluid, and the greater salt concentration, the smaller conversion oscillation frequency. The influence degree of Salt (NaCl) on the rheology of polymer solution is less than calcium (CaCl2) and the polymer HPADA is affected more than HPCBA.The study of light scattering to different hydrolysis degrees of HPCBA and HPADA shows that:in aqueous solution, with the increase of hydrolysis degree, the value of Mw keeps almost constant,<Rg>,<Rh> and<Rg>l<Rh> increase first and then decrease, while the <Rg>/<Rh> is less than1. In salt water, for the polymer of HPCBA-30and HPADA-40, the Mw also keeps almost constant,<Rg>,<Rh> and<Rg>/<Rh> reduced first and then slowly rose with the increase of salt concentration whether it is NaCl or CaCl2、and the<Rg>/<Rh> is less than1all the time. Moreover, the effect of NaCl on the structure of the polymer solution is less than CaCl2and the Mw,<Rg>,<Rh> and<Rg>/<Rh> of HPCBA is lower than HPADA.