Mechanism Of Association Of Hydrophobically Associating Water-soluble Polymers In Porous Media

Hydrophobically associating polymer (HAP) is a new and ideal polymer at present, which has the characteristics of salt -resistance, thermal endurance and shear-resistance. Its unique properties have made it the trend and direction of the future development of polymer in the world oil industry, especially in the field of tertiary oil recovery.Nowadays, most research results have shown that, microscopically, blow the CAC, intra-molecular association will occur the HAP solution; while above CAC, intermolecular association occurs instead, forming dynamically physical cross-linked network structure in the HAP solution .As a result, the fluid mechanical volume is increased, as well as the viscosity of the solution.Due to this association reaction, the dynamically physical cross-linked network of the super-molecular structure can be easily destroyed on the condition of shear, therefore the solution exhibits typical pseudo-plastic behavior; however, as the shear effect decreases or disappears, the cross-links of macromolecular chains will be formed again, and polymer solution viscosity restores again. Therefore. The polymer shows the unique property of shear-resisting. The addition of small-molecule electrolyte increases the polarity of the solution can enhances the hydrophobically association action, thus making it obviously salt-resistance. At the same time, the solution has a feature of thermal endurance and viscosity increase, which result from the entropy-driving endothermal effect of association. All of the characteristics mentioned above can account for that HAP solution uniquely salt-resistance, thermal -endurance and shear-resistance.Starting at the application of HAP in oil field, the association behavior was investigated in different ways and different angels, and the factors influencing this association behavior in porous media was also studied. And the conclusion was drawn that the condition of the application of HAP in the oilfield is that the CAC of polymer should be lowered further.Therefore, the focus of this paper is on the existence of the association of HAP in the porous media, the description of association behavior and the study on the factors affecting the association behaviors.Through investigation of Hydrophobically associating polymer documents, the association mechanism and influencing factors of which had been obtained under macroscopic condition, after experiment in lab, the critical associating concentration (CAC) was 1000mg/l at 60Cand at 5309.74mg/l salinity for Hydrophobically associating polymer selected and investigated. When polymer solution concentration is above CAC, the characteristics of shearing thinning and shearing resistance exhibited.During the course of study on hydrophobically associating polymer rheological properties .we drew a conclusion that under the condition of simulate oil reservoir, the concentration scope of intermolecular association varies obviously.Employing inter-granule velocity and factor of resistance to study on the characteristics of Hydrophobically associating polymer flowing through in porous media. And the characteristics of shearing thinning and shearing resistance exhibited under macroscopic condition when the concentration is above CAC. And the absorb-resort experiment results indicated that the phenomena mentioned above is not the result from accumulation effect in the porous media, which results from large absorb-resort of Hydrophobically associating polymer molecules. So we can draw a conclusion that hydrophobically associating polymer has shown obvious association behavior in porous media.The further step research results indicated that association behavior of Hydrophobically associating polymer would occur only if the concentration is higher than 1000mg/1 and 1 100mg/1, namely called CAC under the condition of microscope.Research results showed that there exists critical association concentration in porous media for hydrophobically associating polymer, which has close relationship with the surroundings of porous media such as concentration, temperat...