A model for predicting reservoir fracturing pressure of perforated wells after acid damage

Acid damage is an effective technology to solve the problem of high fracturing pressure for the deep, tight, low permeability sandstone reservoirs during fracturing or acid fracturing. A model for quantitatively predicting reservoir fracturing pressure of perforated wells with acid damage was established combining with damage mechanics, fracture mechanics and the finite element theory. The model considered the effects of rock mineral composition, acid type, acid amount and temperature on fracturing pressure. The model was used to quantitatively predict the damage variable and fracturing pressure of the acid damaged formation in the Well DY1 in west Sichuan. The results showed that the higher the acid concentration, the higher the rock damage variable and the larger the rock strength reduction, and it will be more favorable for reducing fracturing pressure. The optimal 15%HCl+3%HF acid was applied and the fracture pressure was reduced by 6.5 MPa successfully, which ensured the following “fracture network” acidation implementation. Field application results agreed with the prediction results, which verified the reliability of the model.