Study On The Interaction Between Cyclodextrin And Hydrophobic Associated Polymer Molecules

Among the thchnologies of enhanced oil recovery, polymer flooding has become the main means in the water flooding reservoirs because of its simple and clear mechanism of displacement of oil with the development of science and technology of macromolecules. Finding out new high-powered water-soluble polymers, improving its properties of heat resistance and salt tolerance, broadening its applied range have become the focus of research in polymer science in the field of oil exploitation. Hydrophobic associated polymers are invented out by introducing tiny hydrophobic monomers to the main chain of PAM, its properties of tackifying and salt tolerance are improved, and so do the displacement. But the solubility is decreased at the same time. So the preparation of hydrophobic associated polymer is influenced, especially on the offshore platform. Shielding the hydrophobic association effect between hydrophobic groups during its dissolution stage and recover them after dissolution to improve its solution rate is the purpose of the research.Hydrophobic association between the hydrophobic groups is the fundamental reason of low water solubility of hydrophobic associated polymer. Hydrophobic association between the hydrophobic groups in the swollen particle decreases the rate of diffusion of polymer molecule, which leads to the formation of gel. Gel will stop the water molecule from permeating into the polymer particle, so, the dissolve time of polymer get longer than some common polymers, such as PAM. Cyclodextrins (CDs) have special molecular structure, which contain hydrophobic lumen and hydrophilic shell. CDs can encapsulate hydrophobic groups to form inclusion with the help of hydrophobic association between the lumen and hydrophobic groups. The formation of inclusion shields hydrophobic association, so the polymer molecule could have a higher diffusion velocity, then the dissolve time can be shorted.Thermal gravimetric analysis, differential thermal analysis, infrared spectroscopy analysis, X-ray diffraction analysis and scanning electron microscope are used to prove the formation of inclusion. The method of resistivity is used to study the influence of dissolve time which determined by the interaction between CDs and polymer AP-P4, three kinds of CDs (α-,β-, γ-CDs) are used and three kinds of concentration (3000mg/L,4000mg/L,5000mg/L) are tested. The results show that β-CDs do the best on decreasing dissolve time, which can be reduced to30min from85min. The stoichiometric ratio of inclusion between the CD and the hydrophobic group is determined from fluorescence analysis, and the ratio is2:1. The equilibrium constants are K1=2222.2L/mol and K2=5000L/mol. But the network structure of polymer solution which it should have is disassembled because of the formation of inclusion.Six different surfactants (CTAB, SDBS, Span60, Span20, OP-10, Tween80) are respectively added to the polymer solution to study the recovery extent and velocity of polymer viscosity. The results show that CTAB did the best, and the retention ratio of viscosity could reach about70%in6.5hours, the viscoelasticity of inclusion solution can be enhanced.