Dynamic Redistribution of Fluids in Porous Media

Purdue University, West Lafayette IN

Investigators

Abstract

Most subsurface activities perturb the natural state of fluids in soil and rock because fluids are often injected, withdrawn or transported through the subsurface. All of these techniques induce changes in the local pressure field that initially perturb a multiphase system into a nonequilibrium condition that, over time, relaxes to steady-state or quasi-static distributions. The relaxation depends on pore-scale processes such as dynamic contact angles, air-water interface geometry, temporal changes in wettability, and local heterogeneities in the porous media. This research focuses on an experimental investigation of the dynamic redistribution of fluids in porous media by connecting internal microscopic perturbations to external macroscopic behavior. The study will assess the contributions of wettability, pore topology and films to the redistribution of immiscible fluids in a porous medium in the transition from dynamic to steadystate/quasi-static conditions. A combination of experimental techniques will be used that include the fabrication of transparent micro-models with built-in electro-kinetic actuators tomanipulate fluids at the pore scale internal to the pore network; the fabrication of 3D transparent micro-models using a new grain deposition method; and the measurement of 2D & 3D fluid distributions using fluorescent imaging and laser confocal microscopy to determine the role of absorbed films, corner fluids and pinned films on static and dynamic relations as a function of dimensionality. Analysis of experimental datasets will determine which competing theories for static and dynamic constitutive relationships are supported by experimental evidence, and whether current theories are sufficient to describe multiphase fluid relaxation. Understanding the scaling of pore connectivity and the hydraulic properties of porous networks is of particular relevance today because of the intense activity in shale-gas which depends on networks of fractures to produce the gas, and because of attempts to sequester carbon dioxide in the subsurface. In addition, contaminant remediation efforts, chemical mixing, and biological tissue growth on synthetic porous media all depend on the complex interplay of geometry with the dynamics of fluids. This research will provide critical testing of theoretical methods used to predict flow and distributions of multiple fluids in porous media, and will enable scientists and engineers to connect interfacial areas, disconnected fluid phases and film geometry to macroscopic hydraulic properties.