Coupled Processes at DUSEL: Unique Possibilities

Coupled Processes at DUSEL: Unique Possibilities

Brian McPherson and Eric Sonnenthal

• hydrogeology and the water cycle

• coupled hydrologic and geologic processes in general

• coupled hydrologic and chemical processes in general

• coupled thermal/hydrologic processes and geomicrobiologic activity

• coupled fluid flow and heat flow

• coupled fluid flow (pressure) and rock deformation (strain)

• coupled fluid flow and chemically reactive transport

• coupled fluid flow and mineralization (mineral/ore formation) processes

Major Coupled Processes to Address at DUSEL

Question: What’s the major benefit to Earth Science of “going underground”?

One Typical Approach to Subsurface Investigations: Use drill-hole data with computer model simulations

Data collectedat bottom of borehole.

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Oil or Gas Well

Courtesy: URL at Atomic Energy of Canada Ltd

Proposed New Approach:

Develop a US laboratory and observatory underground,inside the earth.

Much like surgery permits a physician to examine internal bones and organs recognized on X-rays or CAT scans, NUSL will be a fully instrumented, dedicated laboratory and observatory for scientists and engineers to examine Earth’s interior.

Surface laboratories for core, water, gas, and microbial analyses, experiments, and archives

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Deep Flow and Paleoclimate Laboratory and Observatory

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Induced Fracture and Deformation Processes Laboratory

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Ultradeep Life and Biogeochemistry Observatory

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Deep Seismic Observatory

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Deep Coupled Processes Laboratory: study coupling among thermal, mechanical, hydrological, chemical, and biological processes in the subsurface (injection

and transport experiments at several different depths along highly instrumented and well-characterized fracture/matrix zones)

QuickTime™ and aTIFF (LZW) decompressor

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Some Example Coupled Process Studies

- groundwater and geologic processes in general

- spatial and temporal variation of recharge and its interaction with subsurface flow of groundwater

- permeability and scales of evaluation

- stress-state and permeability (critical stress)

Exploration and sustainability of groundwater is critical for an ever-increasing population:

Courtesy: Colorado Division of Water Resources, Office of the State Engineer

Groundwateris a key component of our water supply!

Fluid Flow and Transport

Characterization of active flow system• Characterization of fracture network• Verification of well and tracer test

models• Recharge to deep groundwater

system• Colloidal and bacterial transport• Paleohydrology

Rationale: fluid flow influences resource recovery, water supply, contaminant transport and remediation

However, what actually happens in the subsurface?

Photo Courtesy: Eric Small, Hydrology Program, New Mexico Tech

Question: What factors control how much water at the surface actually reaches the water table?

•surface topography

•surface geology

•vegetation

•climate

All of these aspects may be measured directly

What if we could instrument the surface to provide “controlled” conditions of infiltration?

Recharge and Infiltration Processes

Photo Courtesy: Eric Small, Hydrology Program, New Mexico Tech

Photo Courtesy: URL at Atomic Energy of Canada Ltd.

And then also instrument the subsurface (e.g., of a very shallow drift or set up inter-drift instrumentation) to capture exactly what happens and observe what factors control how much water reaches depth?

• Permeable faults/fractures are critically-stressed• High permeability maintains hydrostatic pore pressure• Hydrostatic pore pressure results in high crustal strength

Hypothesis: Linking Stress State to Permeability to Crustal Strength.

Coupled THMCB Processes in Fractured Rock

Thermal Hydrologic Mechanical Chemical and Biological feedback to mass and energy transport

• Level of characterization required to successfully model (or scale-up) transport (new geophysical imaging and tracer monitoring technologies)

• Effect of physical and chemical heterogeneity on transport

• Environmental processes affecting transport (e.g. induced thermal or stress changes, mineral dissolution or deposition, gas formation or consumption)

SCALE-OF-EVALUATION

Permeability and other properties of crustal rocks may have different values depending on the scale at which it is evaluated. General quantitative or semi-quantitative relationships between

rock properties and scale are dubious or do not exist.

How do we upscale point (space,time) measurements in a complex geologic system to larger regional processes?

Whole earth - 107 m

Regional scale 106 m

Whole mine experiments - 104 m

Stope, cavity scale - 102 m

Tunnel, shaft scale - 101

Borehole, “laboratory” scale - 10-1 m

Grain, sub-lab scale - 10-3 m

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Regional-Scale Permeability of Powder River Basin,Including the Western Black Hills Area

Modeled Heat Flow

Observed Heat Flow

From McPherson et al., 2001

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Assess permeability variation at different spatial scales, using direct methods from within the rocks, and verify proxy methods typically used to evaluate permeability.

Expanded Capability Offered by DUSEL: Scaling

Some Other Hydrogeologic IssuesGroundwater Storage and Aquifer Sustainability: How sustainable is a given aquifer and why? Paleohydrology: better understanding of paleohydrology and evolving water resource systems? Deep Fractures: Can deep fracture systems be mapped, their origin determined, and can fracture flow processes be better characterized from in situ? Flow in Deep Fractures: Are fractures at great depths closed or do they remain open to maintain deep circulation? Contaminant Cleanup: by setting up mock contamination sites within DUSEL, using benign tracers, we can make direct studies of factors that control contaminant transport in the subsurface.Well Testing Verification: Verification of well testing may be performed within DUSEL by direct measurements and observations within the subsurface. Proxy Methods in General: DUSEL offers an unprecedented opportunity to verify proxy or remote methods. For example, the following are used to provide remote "images" of the subsurface:

seismic testing at the surface satellite-based remote sensing (e.g., presence of water in the subsurface)gravity methods at surfaceelectromagnetic methods at the surfacemany othersDUSEL offers an opportunity to verify these remote methods by direct

observation and measurement.

Coupled Thermal-Hydrologic-Mechanical-Chemical-Biological Experiment Opportunities

• Imperatives– Strong scale dependence– THMCB processes incompletely understood– The role of serendipity in scientific advance

• Approach– Run-of-Mine Experiments (HCB)– Experiments Concurrent with Excavation of

the Detector Caverns (THM)– Purpose-Built Experiments (THMCB)

Large Block Tests Mine-By and Drift Structure

Tests Geophysical Monitoring

– Educational Opportunities

New Opportunities for Analysis of Coupled THMCB Processes: Bringing together geochemists, petrologists,

hydrologists, geophysicists, engineers, biologists

• CO2 evolution and transport• Mineral precipitation/dissolution• Stable isotope fractionation• Permeability evolution• Rates of coupled processes• In-situ monitoring and sensors• Testing of new generation reaction-transport models

Yucca Mountain Drift Scale Heater Test Examples

Priority Attributes of DUSEL for Earth Science and Engineering

1. Long-term access to large (~20+ km3) volume of subsurface in which

geological features are well characterized in three dimensions, including appropriately placed sensing equipment.

2. Ability to access this environment through selective/ choice placement of drill holes, underground workings, laboratories, or observatories. Accessed host rock should reach temperatures of 120°C and waterfilled fracture systems.

3. Ability to modify geochemical characteristics of this environment by introduction of materials into holes or workings. At least one fracture zone should be accessed by multiple holes that are instrumented with an array of samplers for transport studies.

4. If an existing mine is chosen as the DUSEL site, complete access to entire archive of existing data and samples.

EARTH SCIENCE AND ENGINEERING CRITERIA FOR DUSEL SITE

Diverse chemical and physical environments, including:

• Variety of hydrologic environments, such as highly permeable, near-surface soils and alluvium vs. deeper, low-permeability crystalline rocks.

• Variety in groundwater compositions, such as high vs. low salinity, pH, and dissolved gas concentrations.

• Variety of structural environments, especially density and orientation of faults and fractures.

• Variety of geochemical environments, especially in concentration of reduced minerals (e.g., sulfides) vs. oxidized minerals (e.g., hematite).

RECOVERY OF NATURAL RESOURCES

• Water Resources**

• Energy Resources

• Mineral Resources

• Efficient Drilling and Excavation

BENEFICIAL USES OF UNDERGROUND SPACE

• Waste Isolation

• Energy Storage

• Transportation Structures

ENVIRONMENTAL REMEDIATION

• Waste Water

• Remediation of Contaminated Groundwater

WHAT ARE POSSIBLE BENEFITS TO SOCIETY?

UNDERGROUND HAZARDS AND SAFETY

• Earthquake Mechanics

• Mine Safety and Health

• Rock Reinforcement and Support

BIOLOGY AND ENVIRONMENTAL SAFETY

• Global Warming

• Groundwater Cleanup

• Origins of Life

• Disease Control

WHAT ARE POSSIBLE BENEFITS TO SOCIETY?