Influence of Hydrologic Heterogencity on Thermal-Hydrologic Behavior in Emplacement Drifts

Fracture networks have been characterized as highly permeable continuum within the porous rock matrix in thermal-hydrologic models used to support performance assessments of the proposed nuclear-waste repository at Yucca Mountain. Uncertainty and spatial variability of the fracture permeability are important considerations for understanding thermal-hydrologic behavior within the host rock surrounding an emplacement drift. In this paper, we conducted numerical experiments with a number of realizations of intrinsic fracture permeability and examine thermal conditions around an emplacement drift. Peak temperature and boiling duration on the drift wall are used as indices to quantify, the influence of fracture permeability. The variability of peak temperature and boiling duration resulting from small-scale fracture-permeability heterogeneity is compared with the variability resulting from variability of host-rock thermal conductivity and infiltration flux. An examination of rock dryout and condensate drainage shows that small-scale heterogeneity in fracture permeability results in a relatively small range in dryout volume and does not prevent the shedding of condensate through the pillar-separating emplacement drifts

Integrated Geothermal-CO2 Reservoir Systems: Reducing Carbon Intensity through Sustainable Energy Production and Secure CO2 Storage

AbstractLarge-scale geologic CO2 storage (GCS) can be limited by overpressure, while geothermal energy production is often limited by pressure depletion. We investigate how synergistic integration of these complementary systems may enhance the viability of GCS by relieving overpressure, which reduces pore-space competition, the Area of Review, and the risks of CO2 leakage and induced seismicity, and by producing geothermal energy and water, which can defray parasitic energy and water costs of CO2 capture

Double Diffusive Natural Convection in a Nuclear Waste Repository

Abstract -In this study, we conduct a two-dimensional numerical analysis of double diffusive natural convection in an er?lplacement drift for a nuclear waste repository. In-drift heat and moisture transport is driven by combined thermal-and conlpositional-induced buoyancy forces. Numerical results demonstrate buoyancy-driven convective flow patterns and configurations during both repository heat-up and cool-down phases. It is also shown that bounda ry conditions, particularly on the drip-shield surfnce, have strong impacts on the in-drift convective flow and transport

Using Sedimentary Basin Geothermal Resources to Provide Long-Duration Energy Storage

Our prior work developed CO2-Bulk Energy Storage (CO2-BES), which uses geothermal power plants and sedimentary basin geothermal resources to time-shift electricity production. In this study, we investigate the maximum duration over which CO2-BES can time-shift electricity generation because there is increasing evidence that, in addition to shorter-duration energy storage approaches, like batteries, energy storage approaches capable of time-shifting electricity generation over long-durations (>10 hours) or even over seasons will be needed in future decarbonized electricity systems. We use an integrated model that we developed and characterized with specific facility-level assumptions to simulate CO2-BES operation and find that a CO2-BES facility operating under these specific assumptions can time shift electricity over durations of at least one week and likely multiple weeks. Time-shifting electricity generation over longer durations (e.g., one month) depletes subsurface overpressure enough that brine flashes in the production well, but durations longer than a couple weeks are likely possible with different facility-level assumptions. Towards this possibility, we conclude with a few ideas for future work that could enable seasonal energy storage with CO2-BES. Overall, this study suggests that CO2-BES specifically, and sedimentary basin geothermal resources generally, can provide long-duration energy storage and show promise for providing seasonal energy storage

Pre-injection Brine Production for Managing Pressure in Compartmentalized CO2 Storage Reservoirs

AbstractWe present a reservoir management approach for geologic CO2 storage that combines CO2 injection with brine extraction. In our approach, dual-mode wells are initially used to extract formation brine and subsequently used to inject CO2. These wells can also be used to monitor the subsurface during pre-injection brine extraction so that key data is acquired and analyzed prior to CO2 injection. The relationship between pressure drawdown during pre-injection brine extraction and pressure buildup during CO2 injection directly informs reservoir managers about CO2 storage capacity. These data facilitate proactive reservoir management, and thus reduce costs and risks. The brine may be used directly as make-up brine for nearby reservoir operations; it can also be desalinated and/or treated for a variety of beneficial uses