GRC 2003: Great Basin Geothermal GIS

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Exploration for Geothermal Resources Field
Techniques GSN Chapter Meeting, Winnemucca, NV
Jan. 14, 2009
Mark Coolbaugh, Lisa Shevenell, Chris Sladek,
Chris Kratt, Jim Faulds, Greg Arehart, Rick
Zehner Great Basin Center for Geothermal
Energy University of Nevada, Reno
Funding DOE Financial Assistance Award
DE-FG36-02ID14311 and University of Nevada, Reno
Applied Research Initiative Grant
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A Boom Has Started in Geothermal Exploration and
Development
Salt Wells geothermal plant under construction,
ENEL
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Western US has a remarkable variety of
world-class geothermal resources
Cascades Mt. Meager
Triple Junction The Geysers
Hot Spot Yellowstone
Cascades Mt. Lassen
Step Overs in San Andreas Salton Sea, Cerro
Prieto
Geothermal (Heat Flow) Map of North
America Blackwell and Richards, 2004
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There is a huge opportunity for finding more
geothermal systems in the Great Basin

• 1) Many blind resources
• 2) They can occur over a large area
• 3) It is challenging to find their exact
  location
• 4) Exploration not been as thorough as for Au
• - economics, leasing difficulties

Blue Mountain
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The best evidence that hidden geothermal
resources remain to be discovered in the Great
Basin many significant discoveries are being
made now, even though geothermal exploration is
just getting re-started
Blue Mountain, Humboldt County, Nevada Most
recent production well (not pictured) flows at
gt200C
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Grass Roots Exploration Recent Geothermal
Discoveries
McGinness Hills Tungsten Mtn Pyramid
Lake (3 areas) Teels Marsh Rhodes Marsh
Silver Springs
UNRs experimental participation in grass-roots
exploration has brought in 7.5 million in added
BLM lease auction sales in 2007 and 2008 (and
more is on the way)
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What is a geothermal reservoir?

• 1) High Temperatures
• 2) Fluid and Permeability
• 3) Heat Exchange between rock
• and fluid below surface
• - the zone of water-rock heat transfer is the
  
• geothermal reservoir

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Geothermal Education Office
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Injection Wells
Production Wells
Geothermal Education Office
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Two types of Geothermal Systems (Koenig and
McNitt, 1983 Wisian, Blackwell, Richards, 1999)
Magmatic Geothermal - associated with
youthful, typically felsic, volcanism
White Island, NZ
Amagmatic Geothermal Systems - associated
with high heat flow and recent faulting
Dixie Valley, NV.
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Magmatic-heated systems, compared to amagmatic
systems, tend to have
1) higher temperatures at shallower depths 2)
have higher 3He/4He ratios (deeper mantle or
magmatic source) 3) have higher concentrations
of some trace elements - As, Li, B, Cs -
possibly contributed by magmas
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Conceptual Model of an Andesitic Volcano
Slide from Joe Moore, 2006
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Multiple reservoirs can occur in one geothermal
system
1st or 2nd most productive geothermal reservoir
in Nevada
Shallower lower temperature reservoir
Johnson and Hulen, 2005
Deeper, higher temperature reservoir
Steamboat Springs, NV
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Schematic fluid flow in a Great Basin amagmatic
geothermal system
Slide courtesy Greg Arehart
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Favorable Structural Environments in the Great
Basin from Faulds et al., 2006

• Features indicative of intersecting, terminating,
  and overlapping fault systems
• Steps in range fronts (Hot Creek, Nye County)
• Interbasinal highs (Salt Wells, Steamboat, Sou
  Hills)
• Ranges of low, discontinuous ridges (Hot Spring
  Mts, Terraced Hills)
• Lateral termination of ranges
• Termination of WL strike-slip faults

Slide adapted from Faulds et al., 2006
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1)
2)
Shallow Outflow Plumes, both a curse and a
blessing After D. Blackwell et al. and C.
Williams
3)
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Advanced argillic alteration
Steam vents
Hot springs
Dixie Meadows, Churchill County, NV
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Shallow temperature anomalies
Desert Queen area, looking south
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Surface Features Related to Geothermal Activity
- hot springs, fumaroles, mud pots - shallow
temperature anomalies - gas discharge zones -
anomalous spring/groundwater geochemistry -
hydrothermal eruption breccias/craters - mineral
deposition silica, calcium carbonate, sulfates,
borates - hydrothermal alteration advanced
argillic alteration - fault scarps - vegetation
anomalies - young volcanic rocks
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Surface Features Related to Geothermal Activity
shallow temperature anomalies
Salt Wells, NV has been considered a blind
geothermal system, but detailed mapping reveals
surface evidence of geothermal activity
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One of the best surface indicators of geothermal
activity is young felsic volcanism
Limited favorability basaltic cinder cone,
Silver Peak, NV
In the Great Basin, nothing spatially correlates
better (thermal features excluded) with
geothermal activity than the presence of young (lt
1.5 Ma) rhyolitic volcanic rocks
Very favorable Young rhyolite dome, Mono
Craters, CA
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The most obvious surface geothermal features are
hot springs and fumaroles
Great Boiling Hot Spring, Gerlach, NV.
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Typically, cooling associated with near-surface
boiling will limit the temperatures of geothermal
features to lt100C, but the presence of
significant steam discharges or mud pots
indicates the presence of a subsurface geothermal
fluid with temperatures gt100C
Steam vents at Bradys Hot Springs, Nevada
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Bradys Hot Springs, NV
Mud pots form from the condensation of acid steam
below the surface and are characterized by
advanced argillic alteration, low flow rates
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Steamboat Springs, south of Reno, NV.
Advanced argillic alteration above original water
table
Hot spring siliceous sinter terrace
The relative location of steam-derived advanced
argillic alteration and hot-spring derived
siliceous sinter can provide clues to the
location of upwelling thermal fluids
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Sometimes non-thermal travertine springs occur on
the margins of geothermal systems
Mt. Meager, B.C.
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Photo Jack Stewart
Hydrothermal eruption craters North Valley, NV
Stewart Roddy, 2002, NBMG Rpt OF02-4. 80 m,
100 m dia.
Other known eruption craters in amagmatic
geothermal systems 1) Surprise Valley 60 m
dia. x four 2) Rye Patch 60 m dia. x one
Steam vent
Dixie Valley 180 m dia. x two
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South fumarole area, Dixie Valley, NV blue line
crater wall red circle fumarole red polygon
vegetation anomaly
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WARM GROUND Thermal outflow zones can produce
extensive areas of warm ground without hot
springs or vegetation anomalies
Blind geothermal system at Teels Marsh, Mineral
County, NV
Quaternary strike-slip fault
Displaced landslide toe
Temperatures are as high at 65C (150F) at 9.5
meters below surface, with no surface expression
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Playa fed by geothermal groundwaters -
temperature up to 67C (153F) at 12 in. below
surface - no thermal springs or vents are
present
Salt Wells, NV.
85C (185F) at 1 meter depth
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Rule of Thumb Siliceous sinter indicates a
subsurface geothermal fluid temperature ? 180C
Sinter with cinnabar Steamboat Springs, NV
Sinter terraces
Beowawe, NV
Transformation with Time opal A opal
CT/cristobalite chalcedony Process takes 10
to 50 thousand years (Herdianita et al., 2000)
Rotorua, NZ
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Sulphur Hot Springs near Ruby Mtns, NV
Geyserite is an indicator of proximity to geysers
and/or boiling or near-boiling springs
Steamboat Springs, NV
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Silica shows a predilection for carbonaceous
material
Silicified plant material Simav-Eynal, Turkey
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In low-flow rate springs and seeps, siliceous
sinter may not form, but other types of surface
and near-surface silicified materials can still
be diagnostic of high-temperature geothermal
activity
Silicified surface/near-surface materials are
extensive at Salt Wells, NV, although true sinter
is rare
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Salt Wells, NV
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Silicified gravels with opal veins
Salt Wells, NV
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Silicified shoreline sands
Salt Wells, NV
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Root casts in opalized sand, Bradys Hot Springs
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(No Transcript)
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unsilicified colluvium
tufa
Lake Lahontan age Silica old high-temp Geothermo
meters current high-temp
Salt Wells, NV
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Salt Wells, NV
Fossilized opalized root casts
Actively forming opalized root casts
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Silicified filiform algae, Salt Wells
Modern and fossilized examples of algae in
thermal waters, Salt Wells, Dixie Valley, NV.
Dixie Valley
Live hot spring filiform algae, Salt Wells
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Framboidal pyrite in opalized root casts
Jarosite coatings are common on opalized root
casts at Salt Wells
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Opal can sometimes form without high-temperature
groundwater
Rainbow Ridge Opal Mine, NV silica is believed
to have been leached from siliceous ash by
groundwater and redeposited by replacing wood
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The presence of late-Tertiary diatomite beds in
Nevada illustrates that conditions favoring
widespread surficial deposition of silica can
sometimes become widespread without requiring
direct involvement of thermal fluids
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Travertine forms around some thermal springs but
it can also form around non-thermal springs.
Sou Hot Springs, NV
Dianas Punch Bowl, NV
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Tufa towers form by reaction of Ca in groundwater
with CO2 in lake water (in this case, former Lake
Lahontan, western NV)
Astor Pass
Smoke Creek Desert
Pyramid Rock
Needle Rocks
Tufa towers, Pyramid Lake Reservation Reservoir
temps 130-170 C
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Evaporite Minerals can be valuable surface
geothermal indicators Na and Ca sulfates
mirabilite, thenardite, gypsum Borates
tincalconite, borax, teepleite, and others
borax / tincalconite
Borax crusts around spring at Rhodes Marsh,
Mineral County, NV
Groundwater Boron
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In desert settings, evaporite crusts can form
without associated surface discharges of water
Calcium and sodium sulfate crusts in a 3 km
long and up to 0.5 km wide area in the Smoke
Creek Desert
Presence of geothermal system evidenced by 49C
artesian well
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Dixie Comstock Mine, NV
Boiling artesian geothermal well, maximum temp
at depth 196C
View width 0.5 cm
Naumannite (Ag2Se) - electrum vein
Native gold - hematite vein
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Surface Exploration Methods
Now that we have models of geothermal reservoirs
and know what to look for in the field, the next
question is how to explore for them most
efficiently.
Bedded sinter, McGinness Hills
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Remote Sensing Diagnostic Spectral Features
siliceous sinter carbonaceous travertine/tufa sulf
ate and borate evaporites hydrothermal alteration
(clay) thermal anomalies
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Remote Sensing for mapping mineralogy and thermal
anomalies
Hymap 3-5 meter
Nixon, NV
Image from Greg Vaughan
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Smoke Creek Desert, Pyramid Lake Paiute
Reservation - discovered during
reconnaissance geothermal exploration
large sulfate anomaly detected with
hyperspectral imagery
systematic spring and well sampling program
Estimates of geothermal reservoir temperature
148-165C
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Spring and Wells Temp Surveys Hot springs and
seeps can be difficult to find in dry desert
climates, where smaller thermal springs and seeps
are sometimes ephemeral, appearing only during
wetter, cooler winter months
Examples from Salt Wells, NV
It took a week to find 7 groups of hot springs
over a 5 km zone in the Salt Wells area, NV
Borax Hot Spring, 81C
Unnamed (unknown) hot springs, 57C, north end
Salt Wells
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Spring and well sampling for temperatures and
geochemistry
Finding the upwelling zone in a wetland can be
difficult, but is important in order to get
accurate temperatures and geochemistry
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K-type thermocouple connected to Data Logger
(with digital storage capability)
Advantages cheap and rugged Disadvantage poor
calibration
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Resistance temperature devices (RTDs) with
platinum resistors (data logger on left)
Advantage electronics insensitive to
temperature Disadvantage more fragile than
K-type thermocouples
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For measurement of temperatures in existing
wells, this equipment pays for itself very quickly
Depth meter
Down-hole temperature probe with 2,000 ft of wire
cable and platinum RTD with temperature-resistant
seals
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Fluid Geochemistry Sampling of spring and well
waters 1) Major, minor, and trace element
compositions 2) Isotopic signatures
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Wet climates and thick vegetation can conceal hot
springs and gas discharges by way of rapid
dilution
Meager Mountain area, British Columbia
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Hidden geothermal system, Three Sisters area,
Oregon, USA
Stream water geochemistry (Cl and SO4) used to
pinpoint geothermal discharges
Slide courtesy Chuck Wicks, USGS
Geochemistry by Ingebritsen et al.
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Fluid Geothermometers
1) Silica geothermometers - solubility of silica
increases with temperature - quartz chalcedony
amorphous silica geotherm. - dependent on T,
pH - sensitive to dilution, re-equilibration 2)
Cation geothermometers - solubility of K-
feldspars relative to Na-Ca feldspars
increases with increasing T - Na-K Na-K-Ca
Na-K-Ca-Mg geothermometers - sensitive to
dilution, re-equilibration
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Historically, the use of geothermometers has been
restricted to thermal waters, but they can also
be applied to cooler waters if appropriate
caveats are used
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Another fundamental exploration tool involves the
Mapping of Thermal Anomalies, which has been
responsible for many geothermal discoveries over
the years
Down-hole temperature gradient measurements are
important for geothermal exploration
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Surface temperatures can be mapped with remote
sensing
Geothermal Power plant
N
Onion plant
1 km
Bradys Hot Springs Fumarole/Warm Ground
Anomalies mapped with ASTER thermal infrared
satellite imagery
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Daily temperature variations at the surface damp
out quickly with depth.
surface
1-meter-depth
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Early champion of the concept Dennis Trexler

• Basic Equipment List
• 1) Modified rods
• 2) Demolition hammer
• 3) Portable generator
• 4) ATV
• 5) RTDs data logger
• 6) GPS unit

Bottom ends of rods are welded close
hard-faced
2.2 m lengths of schedule 80 seamless steel
pipe (0.54 OD, 0.302 ID)
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Black lines 1C contours on 2-meter temperatures
Coolbaugh et al., 2007, Stanford Geothermal
Workshop
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Spring geotherm. Na-K-Ca-Mg 192C
(378F) Quartz 118C (244F)
65C (150F) at 9.5 m
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Rhodes Marsh, Mineral County, NV. Red
strike slip fault Black normal fault
opalized sands
springs/wells
Warm well with borates 155C / 162C cation/qtz
geotherm. (311F/324F)
361 ppm Cl, 414 ppm SO4 sampled 2005
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Geophysical Surveys
Gravity Magnetics Electrical Seismic Microseis
mics InSAR
Horizontal gravity gradient
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Pirouette Mtn and 11-Mile Canyon Geothermal
Areas Dixie Valley, NV
The Pirouette geothermal area occurs near the
center of Dixie Valley, where geologic mapping
provides only limited information.
Niti Mankhenthong thesis
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A detailed gravity survey by Niti Mankhenthong
(M.Sc. Thesis in progress, UNR) provides much
structural information to help explain why the
Pirouette geothermal system occurs where it does.
Mankhenthong et al., 2008
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Southwest Smoke Creek Desert
Horizontal gravity gradients help define a zone
of structural splaying near a step over in a
range front fault
Near-surface upwelling zone at range front
step-over with tufa towers
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ELECTRICAL METHODS widely useful because
- geothermal waters have relatively high
conductivities (salinities) - hot water is more
conductive than cold water - argillic
alteration characterizes the upper portion of
many systems
From Keller Frischknecht, 1966
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ELECTRICAL METHODS include
- Resistivity - Time Domain Electromagnetics -
Magnetotellurics - Self Potential
Caution in Great Basin saline playa groundwaters
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Resistivity map, Ohaaki
Ocean
50 km
Waiotapu
Ohaaki
Wairakei
Lake Taupo
Resistivity map, TVZ
Slide adapted from Arehart
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Slide courtesy Bill Cumming
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VES vertical electrical sounding
Slide courtesy Bill Cumming
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Slide courtesy Bill Cumming
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SEISMICS and 3-D reflection
- key tool in petroleum exploration - has been
adapted for use in Great Basin - more frequent
velocity calculations - Optim, UNR Seismo
Lab - has some good success stories
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• Dixie 2.5D Model
• Further analysis of production related structure
  revealed a basin-ward synform, or half graben,
  that directly correlated with location of
  production and injection wells.
• Velocity analysis also revealed less dramatic
  basinward structure in area of Line 10.

From Honjas, 2002
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From Blackwell et al., 2007
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Geothermal Drilling
1) Temperature gradient drilling 2) Slim
holes 3) Production wells
Photo Frank Baumann
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FINAL COMMENTS
1) Exploration tools for geothermal are similar
to those used for precious metals exploration,
with important differences 2) Many
opportunities remain for finding more geothermal
systems in the Great Basin
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The End