Rheological property and viscosity variation mechanism of variable viscosity diverting acid based on betaine

Key words:  betaine  variable viscosity diverting acid  rheological property  viscosity variation mechanism  core flow

Abstract:

Based on visco elastic surfactant theory，a new variable viscosity diverting acid ( VVDC) with good performance was developed, and its micelle structure characteristics and viscosity variation property were analyzed. The influence of shear rate on the concentration o￡ oleic amide propyl betaine, pH and rheological property of VVDC for different temperature was studied. The influence of the pH on micelle structure was discussed, and the viscosity variation mechanism of VVDC was obtained. The results show that the micelle structures of VVDC in the HC1 of 10%, 5% , 2% ( mass fraction) are globular, rod and the transitional form between globular and rod, and wormlike respectively. The apparent viscosity of VVDC increases with the acid concentration decreasing，and it has the dilution shearing feature when the oleic amide propyl betaine concentration is higher than the critical micelle concentration. During the acidizing process，the pressure of VVDC is reduced after increasing. And the flow of acid turned into the low-medium permeability reservoir, which does no harm to the reservoir.