Pore-scale experimental study on fluid injection into two-dimensional deformable porous media

Abstract

Fluid injection into a deformable (or soft) porous medium often results in the deformation and/or displacement of hosting solids, which in return, influences the transport of injected fluid. This study presents a summary of recent pore-scale experimental efforts that attempted to advance our understanding on the hydro-mechanical coupling at the pore scale. Our experimental study examines the effects of various fluid flow conditions, including miscibility, viscosity, injection rate, as well as mechanical stiffness/compression on the fluid-driven deformation and concurrent fluid transport more comprehensively. We also introduce four particle-level pressure terms, the yield (Py), fracture (Pf), capillary entry (Pc), and viscous drag (Pv) pressures, as primary indicators to properly capture the observed regimes of fluid-driven deformation and fluid transport, in addition to the traditional capillary and mobility numbers. The collected test results reveal that the single-phase fluid flow causes the fluid-driven solid deformation only when Pv/max(Py, Pf) ≥ 10−2, and its prevalent shape is volumetric deformation around the injection port. The two-phase fluid flow renders a volumetric deformation pattern when 10−5 < Pv/max(Py, Pf) < 10−2 and 10−2 < Pc/max(Py, Pf). Whereas, it causes fracture-like solid deformation when Pv/max(Py, Pf) ≥ 10−2 and Pc/max(Py, Pf) ≥ 10−2. A complex transition from the volumetric to fracture-like deformation, and then to pore invasion (without any noticeable solid deformation) may occur in a single porous medium if the injected fluid is low viscous and the local effective stress is relatively small. Furthermore, the results reveal a good correlation between the maximum inlet pressure and the magnitude of fluid-driven deformation. Lastly, a comparison of fluid injection energy is provided for those different regimes of fluid-driven deformation and fluid transport. This study provides unique pore-scale experiment results on flow-induced deformation and suggests criteria based on dimensionless parameters with the particle-level pressures, which advances our understanding and prediction capability on hydro-mechanical behavior associated with fluid injection. The observations from this study have implications for many geological and biological systems that are associated with porous materials and fluid injection, including geologic carbon sequestration and convection-enhanced drug delivery.