During characterization efforts of complex sites and geologies, it is important to estimate material properties efficiently and robustly. We present data and modeling related to the heat of wetting process during spontaneous imbibition, as observed in zeolitic tuff. The heat of wetting is due to adsorption of liquid water and water vapor to an oven-dry core sample and results in an observable temperature rise. The fitting of numerical models to imbibition observations allows simultaneous constraint of single-phase (porosity, permeability), two-phase (van Genuchten m and alpha), thermal (thermal diffusivity), and transport (tortuosity) properties from a single imbibition test. Petrographic analysis informs how microstructure connectivity and pore-lining phases affect the imbibition process. Estimating multiple properties simultaneously from a single test on a core sample helps ensure consistency in interpreted material properties. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525 (SAND2023-07021A).

The Brine Availability Test in Salt (BATS) is a field heater test being conducted in the bedded salt formation at the Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM. BATS is focused on exploring brine availability as part of a wider investigation into the disposal of heat-generating radioactive waste in salt. Brine has the potential to transport radionuclides, corrode waste forms and packages, reduce criticality, and pressurize porosity to resist closure through salt creep. In BATS, two identical arrays of horizontal boreholes were constructed in an experimental drift, 650 m below ground at WIPP. In each array, 13 observational boreholes were installed around a central borehole. One of the two array was heated, and the other array was left at ambient temperature. During the first heating phase (January to March 2020), the 750 W heater ran for 4 weeks. The central boreholes included dry nitrogen gas circulation behind a packer. The gas stream removed moisture which flowed into the boreholes. The gas stream was analyzed in-drift for stable water isotopes using a cavity ringdown spectrometer and gas composition using a quadrupole mass spectrometer. The satellite boreholes in each array included numerous thermocouples, electrical resistivity tomography (ERT) electrodes, acoustic emissions (AE) piezoelectric transducers, distributed temperature and strain fiber optics, and a cement seal exposure tests (both sorel and fly-ash base concretes). Cores from the boreholes were X-ray CT imaged for mineralogical and fracture distribution. We present an overview of the first phase of the test, and illustrate key data collected during the first heating cycle. Follow-on tests in the same boreholes will include gas and liquid tracer tests and additional packer-based gas permeability testing. New boreholes for the next round of BATS in 2021 are being planned.

We present an approach to uncoupling the pair of transient governing equations used in electrokinetics (i.e., streaming potential and electroosmosis). This approach allows for the solution of two uncoupled “intermediate” equations, then the physical solution is found by recombination of these intermediate potentials through a matrix multiplication. We present numerically stable expressions for the coefficients, and an example showing electrokinetics arising from pumping a fully penetrating well in a confined aquifer, surrounded by insulating aquicludes. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. (SAND2019-8712 A)

We present preliminary results from an electrokinetic laboratory rock characterization approach, which uses electroosmosis and streaming potential to estimate permeability. The device has two modes. In its first mode it measures differential pressure across a sample while applying electric current or acoustic pressure, while in its second mode it measures voltage across the sample when applying electric current or acoustic pressure. The two modes result in estimates of the electrokinetic coupling coefficients, which can jointly be used to estimate the permeability of the sample. Our collaboration includes analytical and numerical approaches simulating aspects of the experiments being carried out in the laboratory at Sandia. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.