Utilizing Field Data and Numerical Modeling to Constrain Reservoir Parameters During a Salt Heater Test

Abstract:

Brine availability in salt has multiple implications for the safety and design of a nuclear waste storage facility. Brine migration is a potential off-site radionuclide transport vector, brine leads to corrosion of metallic and glass waste forms and waste packages, chloride in brine can reduce criticality concerns, and accumulated brine can provide back-pressure that resists long-term creep closure of porosity associated with mining the repository. In order to improve understanding of brine migration in heated salt, borehole heater experiments are being conducted at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico. While undisturbed rock salt is uniformly low porosity and permeability, upon excavation a damaged region develops surrounding the excavation. This region is referred to as a "disturbed rock zone" (DRZ) and introduces significant heterogeneities in the near field which impacts the effectiveness of the salt as a storage and disposal medium. Since brine transport is the primary off-site radionuclide transport vector understanding heat and mass transport within the DRZ is critical for characterizing the long-term behavior of the system. As a result, this study investigates the thermal and hydraulic properties of both undisturbed salt and the DRZ by matching both temperature and brine output measurements from the field during a salt heater test. The methods presented here illustrate the effectiveness of utilizing both thermal and hydraulic field data to constrain numerical models for parameter estimation. These results will be utilized to inform future high-resolution, 3D modeling studies of the salt heater test.

SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

SAND2020-7627 A