Preparation and performance of the variable viscosity acid

Acidification is an important means to increase the yield of oil and gas wells, and the key to successful acidization is removing formation damage. In heterogeneous reservoir, acid will give priority to high permeability layer and it is difficult to enter the low permeability layer, so even acidification can not be achieved. Due to the polymers in conventional variable viscosity and acid gel, it is difficult for gel to break after acid-rock reaction and the residue and insoluble in residual acid will seriously damage low permeability reservoir. Therefore, a viscoelastic surfactant JX was made indoor, and it is used to prepare a new variable viscosity of viscoelastic surfactant acid VDA-JX, and its performance was evaluated. Laboratory study results show that the viscosity of the acid with the acid concentration increases firstly and then decreases, when the acid concentration reach 13%, the maximum viscosity occurs which can be achieved to 350 mPa·s, meeting temperature resistance and shear resistance demands in the process of acidification, meanwhile, the gel breaking time is short, acid is easy to flow back, and is stratified with the kerosene after gel breaking, so it doesn't pollute the reservoir.