Simulation Study of Acid Fracturing Initiation with Consideration of Rock Mechanics Parameter Variations

Abstract Deep carbonates hydrocarbon resources are abundant and hold significant potential for sustainable energy development in future. Acid fracturing is an effective technology for carbonate reservoirs development; however, it is difficult to predict the rock initiation pressure for acid fracturi...
Ausführliche Beschreibung

Abstract Deep carbonates hydrocarbon resources are abundant and hold significant potential for sustainable energy development in future. Acid fracturing is an effective technology for carbonate reservoirs development; however, it is difficult to predict the rock initiation pressure for acid fracturing, which restricts the efficient development of carbonate reservoirs. In this paper, the changes of elastic modulus, Poisson's ratio and tensile strength of carbonate rock samples are tested under different acid treatment duration and temperature, and rock mechanics parameter evolution models for acid treatment rocks are obtained by experimental results fitting. Then, the evolution models are embedded into fracturing finite element calculation program to predict fracture initiation pressures accounting the dynamic evolution of rock mechanics parameters for acid fracturing. The error between the predicted fracture initiation pressure and the field data is only 0.46%, which shows a very good accuracy. The study shows that the elastic modulus, Poisson's ratio and tensile strength of carbonate rocks decrease with the increase of acid treatment duration and temperature. The changes of acrid rock mechanics parameters have a significant impact on fracture initiation pressure, and the evolution of elastic modulus and Poisson's ratio is the main controlling factor for fracture initiation pressure. Under the same reservoir temperature, long acid treatment duration could enlarge acid swept area and lower fracture initiation pressure; under the same acid treatment duration, high reservoir temperature strengthen rock dissolution by acid, and the fracture initiation pressure has a slight increase. Ausführliche Beschreibung