Abstract

Injection of fluid into a porous material will drive mechanical deformation when the fluid pressure becomes comparable to the stiffness or strength of the solid skeleton. This has applications ranging from the geological storage of carbon dioxide to the recovery of natural gas from shales via hydraulic fracture. However, these problems are notoriously inconvenient to study in a laboratory setting because of the difficulty of accessing the deformation field in a high-pressure system. Here, we present a new experimental model system for performing dynamic, high-resolution measurement of poromechanical deformations: Fluid injection into a packing of soft particles. Using high-resolution imaging, we measure the full deformation field and we study the dynamic interplay between grain-scale rearrangements and macroscopic poromechanical response. We show that the deformation involves a complex combination of rearrangement, shear failure, and the quasi-reversible storage and release of elastic energy. Despite the grain-scale complexity, we find that a minimal mathematical based on poroelasticity with viscous dissipation is able to capture certain macroscopic (continuum-scale) aspects of our experiments.