Experimental Study on Hydrophobically Associating Hydroxyethyl Cellulose Flooding System for Enhanced Oil Recovery

A hydrophobically associating hydroxyethyl cellulose (HAHEC) used for enhanced oil recovery (EOR) was studied in the present study. The effects of HAHEC concentration, temperature, and shear rate on apparent viscosity of HAHEC solution were explored. Results show that, because of the hydrophobic association of HAHEC molecules and the formation of supramolecular aggregates, the viscosifying performance of HAHEC is obviously better than that of HEC. But the apparent viscosity of HAHEC solution is sensitive to the temperature and it declines significantly especially when the temperature is less than 50 degrees C. HAHEC solution also has satisfactory shear resistance performance, and its apparent viscosity can basically return to the initial value after withdrawing severe shear action. Moreover, HAHEC shows favorable surface and interfacial activities because of the adsorption and arrangement of HAHEC molecules onto a water/air surface and water/oil interface. Sand pack core experiments were conducted to investigate the EOR ability of the HAHEC flooding system; results display that both the resistance factor and the residual resistance factor of HAHEC solution in cores are higher than those of HEC solution. Favorable EOR performance of the HAHEC flooding is proved, and high incremental oil recovery can be achieved with the application of optimized injection concentration, injection rate, and injection slug size after initial water flooding. In addition, the emulsification phenomenon is obvious during the HAHEC flooding because of the favorable surface and interfacial activities of HAHEC.