How multilayered rocks seal the fate of fluid-filled fractures

Understanding fluid transport and storage in low permeability rocks is essential to the safe long-term carbon dioxide sequestration in geological formations. In this study, we investigate the behavior of liquid-filled fractures within stratified media, employing laboratory-scale experiments. Our focus lies on analyzing the fracture geometry resulting from the injection of a low-viscosity fluid into a hydrogel block composed of two layers exhibiting different levels of stiffness, characterized by different Young's moduli. The experimental results reveal that the fracture geometry depends on the initiation layer. Fractures formed within a soft layer exhibit restricted propagation, failing to penetrate the neighboring stiff layer.

Conversely, fractures initiated within a stiff layer exhibit rapid transfer into a softer layer upon reaching the interfacial region. To explain these experimental observations and shed light on fracture propagation mechanisms within geological formations, we present scaling arguments. The theoretical model provides a deeper understanding of the experimental outcomes, offering insights into the complex nature of fluid propagation and storage within layered media.