INVESTIGATION OF WING CRACK FORMATION WITH A COMBINED PHASE-FIELD AND EXPERIMENTAL APPROACH

Fractures that propagate off of other weak slip planes are known as wing cracks, and may play important roles in both tectonic deformation and fluid flow across reservoir seals. Previous numerical models have produced the basic kinematics of wing-crack opening, but generally have not been able to capture fracture geometries seen in nature. A challenge in simulating wing crack formation is to capture the rotation of the fracture during deformation. Here we introduce and benchmark a phase-field model that is able to capture this rotation leading to curved wing cracks. The phase-field approach is based on a variational method to approximate lower-dimensional surfaces and discontinuities for fractures by employing Griffith’s model. To benchmark the numerical approach we perform physical experiments where we investigate wing crack formation in gelatin during simple shear. We are using a simple elasto-plastic deformation regime so that a meaningful comparison between the models and experiments can be achieved. We compare the fracture geometry, the evolution of the fracture angle as well as the force evolution during fracturing. By bench marking the models with physical experiments, we can show that the numerical assumptions in the phase-field approach do not affect the final model predictions of wing-crack nucleation and growth. Our results demonstrate that the phase-field model is able to capture the characteristics of wing cracks observed in nature and experiments and that it is feasible to implement the formation of wing cracks in large scale phase-field reservoir models.