Fracture Propagation under Poro-thermally Induced Stress using the Displacement Discontinuity method

Abstract

The problem of poroelastic and thermally induced fracture propagation due to transient cooling is important to geothermal and unconventional petroleum reservoir development. This paper considers and solves this problem numerically using two-dimensional displacement discontinuity method. First, we show the stress and temperature distributions on and near a single crack in an elastic domain to demonstrate the effect of transient cooling on the thermally induced stresses near fracture. Then, we consider poroelastic effects in conjunction with thermoelastic stress to illustrate their combined impact on fractures and their propagation. For determination of the crack propagation path, the maximum principal stress criterion is used. Also to increase the accuracy of stress intensity factor calculations, a special crack tip displacement discontinuity element is implemented at the crack tip. Numerical results show that the high tensile stresses due to cooling can lead to formation of secondary fractures perpendicular to the main fracture. The pore pressure effect is expected to have high influence on the determination of fracture path and porothermoelastic field in the geothermal reservoir.