Study On Rheological Properties And Synergistic Effect Of HPAM And

Partially hydrolyzed polyacrylamide(HPAM) is widely used as polymer flooding presently. The oil displacement efficiency largely depends on the viscoelasticity of HPAM solution. The viscoelasticity is a kind of macroscopic behavior of molecule motion in aqueous solution and it is influenced by salinity, ambient temperature and molecular interaction. HPAM exhibits typical weak polyelectrolyte property in aqueous solution and it is sensitive to salinity. Although the XG solution exhibits the characteristics of polyelectrolyte solution, it has especial screwy conformation, thus makes it a good salt resistance. Through macromolecules interplay by blending HPAM and XG solution would realizes the complementation of the properties. This would provide a type of physical modification for polymer oil displacement. In brief, the exploration of variation of molecular interplay under different temperature or other condition in aqueous solution, molecular motion and the solution viscoelasticity behavior could provide fundamental basis for the development of heat-resistant or salt-tolerant polymer oil displacement agent solution.In oscillation and steady state mode, for HPAM and XG solutions, the rheological behavior, relationship between variation of relaxation time and molecular motion unit were explored. The synergy behaviors of HPAM/XG solution were studied and the molecular interaction existed possibly was further proved simultaneously. First of all, ARES G2rheometer was utilized to explore the oscillation and steady state rheological behavior for high molecular weight HPAM solution and XG solution under different concentration and salinity. On the basis of the above data, the corresponding power law equation, first normal stress difference and relaxation time were calculated. Through the analysis of data and we found that XG solution was more salt resisting than HPAM solution and the dispersion of counter ion in aqueous solution had less effect on G’,G",tanδ and first normal stress difference. The different motion units which have different size corresponded to different relaxation time. With rising concentration, the relaxation time spectra become wider and wider due to molecular interaction and it indicated that some more complex motion unit appeared in aqueous solution. Meanwhile, the relaxation time spectrum can be used to indirectly characterize molecular size. Ubbelohde viscometer and rheometer were utilized to explore the synergy behaviors in blending solution. The results showed that it behaved negative synergy when the XG content was less than30%and the change of solvent property held the dominant position, whereas molecular interactions played leading role and greater size motion unit formed when the XG content was higher in blending solution and it showed positive synergy. When XG content was80%, the positive synergy was the most obvious in our measurements. The light scattering measurements also manifested that the hydrodynamic diameter for blending solution which behaved positive synergy effect was greater than one-component solution’s and the mean diameter was4468.3nm. The TG and DTG were carried out to analyze chemical degradation in temperature-rise period and it indicated that there was no obvious chemical degradation when the temperature was less than155℃, the variation of rheological properties mainly caused by molecular interaction and motion active energy. There was obviously exothermic process observed by DSC difference spectra and asynchronous analysis in HPAM/AP-1solution when experimental temperature was from40℃to45℃. The2DCOS analysis for carbonyl under variable temperature conditions also found that some carbonyl-water hydrogen bonding transform into carbonyl-hydroxy or carbonyl-amino hydrogen bonding in these temperature range. The steady-state rheology curves demonstrate that blending solution has the most apparent viscosity in low shear rate when temperature is45℃and it was consistent with the previous discussions.