A Model with pressure decline curve for acid fracturing wells

The pressure decline analysis and evaluating techniques for acid fracturing wells develop quite slowly.When operation of the acid fracturing well is completed,the acid-rock reaction on the fracture face is still going on and generates CO2,which exerts obvious effect on the compressibility of acidizing fluid and residual acid and the pressure response of the acid fracturing well after shut-in.The leakoff mechanism of the acidizing fluid is quite different from that of the fracturing fluid.This paper therefore puts forward a new method to analyze the pressure decline for acid fracturing wells.Based on taking fluid compressibility and strata temperature into account,it deduces the continuity equation of fluid after shut-in,establishes a mathematic model to calculate the fracture parameters in terms of the pressure decline data,shows the solution technique for the mathematic model by matching pressures decline data,and builds the interpretation software to analyze the pressure decline after shut-in.Case analysis shows that strata temperature and fluid compressibility must be taken into consideration to analyze the pressure decline for acid fracturing wells,which will be improved by employing the method that uses computers to fit the pressure decline curve,because it simulates the physical and chemical change in fractures after pumping and the leakoff coefficient and fracture geometry parameters interpreted in this paper are more close to the reality of strata.Therefore,the model and method presented in this paper can provide reliable techniques for evaluating acid fracturing operation and optimizing the acid fracturing design.