Sandia National Labs FY20 LDRD Annual Report

FY20 ANNUAL REPORT

Characterization and sampling of ultralow permeability geomaterials using electrokinetics. Ultralow permeability geomaterials are critical to missions including advanced energy, infrastructure, and nuclear waste disposal. In this project, Sandia, the University of Illinois Urbana-Champaign and Cal Poly San Luis Obispo investigated hydrogeophysical coupling between water movement and electric current flow in tight rocks and developed new transient electrokinetic laboratory methods to sample and characterize properties of fractured ultralow permeability geomaterials (e.g., granite or cement). Characterization of low-permeability rocks – with micron-scale pores – is important for applications like radioactive waste disposal, borehole sealing, water resource management, and CO 2 sequestration. Pressure-driven fluid flow through a porous medium drags along ions, creating a streaming potential. Similarly, applied AC or DC electric current will move ions in the same porous medium, which drags along water, creating an electroosmotic pressure. The team used combined oscillatory tests of these reciprocal effects to estimate steady-state permeability (a parameter of interest in tight rocks) without a traditional Darcy flow test. Sandia PI Kris Kuhlman said, “Leveraging an Academic Alliance partnership, we combined Sandia’s expertise in geomaterials and earth science applications with Illinois’ capabilities to simulate nano- and micro-fluidics, incorporating laboratory, theoretical, and numerical approaches to tackle the electrokinetics problem. The project resulted in journal publications on general approaches to solving coupled multiphysics problems and new insights into the relationship between streaming potential and electroosmosis for a range of pore and path complexities in idealized 2D porous media.” These methods have fundamentally contributed to physical understanding of transient electrical phenomena in rocks, revolutionized Sandia’s ability to understand and control them, and broadly advanced the state of the art. (PI: Kris Kuhlman) Watch the YouTube video. FY20 LDRD Annual Report Project Highlights – Missi n Agility, Technical Vitality, Workforce Dev. Final through a porous medium drags along ions, creating a streaming potential. Similarly, applied AC or DC electric current will move ions in the same porous medium, which drags along water, creating an electroosmotic pressure. The team used combined oscillatory tests of these reciprocal effects to estimate steady-state permeability (a parameter of interest in tight rocks) without a traditional Darcy flow test. Sandia PI Kris Kuhlman said, “Leveraging an Academic Alliance partnership, we combined Sandia’s expertise in geomaterials and earth science applications with Illinois’ capabilities to simulate nano- and micro- fluidics, incorporating laboratory, theoretical, and numerical approaches to tackle the electrokinetics problem. The project resulted in journal publications on general approaches to solving coupled multiphysics problems and new insights into the relationship between streaming potential and electroosmosis for a range of pore and path complexities in idealized 2D porous media.” These methods have fundamentally contributed to physical understanding of transi nt electrical phenomena in rocks, revolutio ized Sandia’s ability to understand and contr l them, and broadly advanc the state of the art. (PI: Kris Kuhlman) Watch the YouTube video.

(Left) Pore-scale flow simulations by the University of Illinois illustrating streamlines around grains of variable shape and orientation. Electroosmosis is stronger in a more tortuous medium, while streaming potential is stronger in a less tortuous medium. (Right) Predicted pressure ( " ) and electrical ( " ) response in space ( " ) and time ( " ) for a harmonic streaming potential test, based on simple analytical solutions using the new uncoupling approach.

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LABORATORY DIRECTED RESEARCH & DEVELOPMENT