Study On Betaine Viscoelastic Surfactant Self-diverting Acid Technology

Viscoelastic surfactant self-diverting acid diversion acidizing technique is a newly developed reservoir stimulation technique,with the advantage of simple preparation,gel breaking easily,small formation damage,slow and lower filtration.When the pH value is about 2,the viscosity of the system increases with the free Ca²⁺,Mg²⁺ chelating with viscoelastic surfactant molecules to make the arrangement of the surfactant molecules changing,then the self-diverting acid turns from the high permeability zone into the low permeability one.The system loses its viscosity by touching with hydrocarbons,water diluting,and mixing with gel breaker. The oleic acid, 3– Dimethylamino propyl ammonia and sodium chloroacetate are used to synthesize the acid amide propyl betaine by amide and quaternary ammonium.In order to better serve the acidizing operation, the rheological analysis of the self-diverting acid is taken,and the effects of the concentration,temperature,pH value,shear and shear history, inorganic ion concentration are measured. The rotating disk reactor is used for the reaction kinetics. And the reaction is dominated by H⁺ mass transfer coefficient; The effect of temperature on the diffusion coefficient doesn't follow Arrhenius law.The reaction rate increases slowly with the temperature rising,when the temperature is above 70oC,the reaction rate increases rapidly.Based on the Darcy law,the diversion criterion is developed.When the self-diverting acid is on the diversion, the log-log curve between Rp and k_o/Φ_o is a line.