Influence of dissolved oxygen content on oxidative stability of linked polymer solution

The influence of dissolved oxygen content on the oxidative stability of a linked polymer solution (LPS) was studied by micro-filtration, dynamic light scattering and viscosity measurements. The results showed that at the same temperature, the degree of the oxidative degradation of the LPS increased and the rapidity of the oxidative degradation was accelerated with the increase of the dissolved oxygen content. Consequently, the size of linked polymer coils (LPCs) of the LPS became small, and the plugging capability of the LPS decreased. At a fixed content of dissolved oxygen, with increasing degradation temperature, almost the same results were observed, namely, an increased degree of oxidative degradation, accelerated rapidity of the oxidative degradation and decreased plugging capacity, with decreased oxidative stability of LPS. At 90 °C, in the presence of oxygen, LPS lost its plugging capability after having been degraded for a period of time. But at 40 °C, LPS with low dissolved oxygen content could be stable for a long time. The decreased plugging ability of LPS after oxidative degradation is mainly caused by the decreased size and number of the LPCs due to the breaking of hydrolyzed polyacrylamide (HPAM) molecule segments and the structural changing of HPAM molecules.

Deformation of Linked Polymer Coils

Linked polymer solution (LPS) is defined as the solution of linked polymer coils (LPCs) dispersed in water, composed of low concentration partially hydrolyzed polyacrylamide (HPAM) and aluminum citrate (crosslinker). In the work, the conformational changes of LPCs under different conditions were investigated by the methods of membrane filtering under low pressure, dynamic light scattering and core flooding experiments. The results showed that in some conditions the LPCs could be compressed mechanically to 1/158.5 of their original volume because of relatively lower HPAM cross-linking. The hydration property of LPCs was similar to that of normal polymer coils. The deformation of LPCs was more restricted than that of ordinary polymer coils under the flow shear stress or the shift of hydration equilibrium caused in the variation of the electrolyte concentration which is responsible for the effective plugging in the throats of porous media when LPCs are used for deep diverting.