The evolution characteristics and the final shape of acid viscosity fingering are influenced by many engineering and geological factors. So that

we used the visual experimental device to explore the change rules under the multifactor. Six factors were considered

those are the concentration of acid

the injection series

the temperature

the construction displacement

the viscosity ratio of the liquid

and the inclination of crack. The fractal dimension and multifractal spectrum width were used to describe the morphological of fingering. It is concluded that the influence degree of each factor on fractal dimension from high to low is in the order of: viscosity ratio

injection series

temperature

acid concentration

construction displacement

and crack inclination. The influence degree of each factor on the multifractal spectrum width from high to low is in the order of: viscosity ratio

crack inclination

construction displacement

acid concentration

injection series

and temperature. In order to achieve the viscosity fingering of acid fracturing

the viscosity ratio should be increased to the value between 100∶1 and 150∶1

the controlled injection series are at level 2 to level 3

and the designed acid dosage is about 0.3. Meanwhile

a large number of pre-liquid was injected to reduce the crack wall’s temperature before the acid injection.