Analysis of near-tip strain field of the propagating fracture through mechanically layered system

ABSTRACT: Subsurface formations consist of mechanically layered systems with stratigraphic layers of varying properties, significantly influencing fracture height growth. This study utilizes SCB tests to examine how variations in elastic properties, strength contrast, and layer dip angles affect fracture trajectories. Additionally, the distance between the layer boundary and the notch tip was varied to assess its influence on fracture propagation. DIC analysis was used to examine the strain-fields near the interface during fracture propagation and interaction. Results indicate that rock modulus/strength contrast and layer dip impact the fracture growth and containment. When a fracture propagates from a soft/weak layer into a stiff/strong layer, DIC results reveal strain development in the stiffer layer at an offset distance from the fracture plane. In contrast, when propagating from stiff-to-soft, fracture crosses into the softer layer without diversion. In soft-to-stiff cases with dipping layers, fracture diversion becomes more likely as dip angles increase, while no diversion was observed in stiff-to-soft cases. Additionally, in soft-to-stiff cases with non-dipping layers, increasing the interface distance from the notch-tip extends the fracture diversion distance along the interface. The findings of this study contribute to better understanding of the influence of stratigraphic layer characteristics on fracture propagation and height containment.