Stress Field and Fracture Propagation Induced by Fluid Pressure Changes

It is well known that the hydraulic fracturing is an indispensable scheme commonly used for fracturing and stimulating hydrocarbon reservoirs. It is, however, difficult to predict the behavior of fracture propagation around boreholes in a medium under regional complicated stress due to a lack of numerical schemes to simulate rock failures. In order to solve this problem of hydraulic fracturing, we have developed a program to simulate fracture propagation due to the hydraulic pressure using an extended finite difference method (X-FEM). Numerical simulations are conducted for a 2D elastic medium having a borehole and a fracture. We confirmed that the orientation of the fracture propagation converges to that of the principal stress. Moreover, the convergence speed could be inversely related to the hydraulic pressure. We also found the time delay of the influence of the hydraulic pressure change to the fracture propagation with non-steady hydraulic pressure condition. We would like to conclude that the orientation of maximum in-situ principal stress and the fluid pressure for fracturing is major parameters to control the propagation of fractures due to increasing fluid pressure. The time delay of the change of the stress field also should be taken into account.