GRC 2003: Great Basin Geothermal GIS

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Prediction and Discovery of New Geothermal
Resources in the Great Basin Multiple Evidence
of a Large Undiscovered Resource Base
Mark Coolbaugh, Gary Raines, Rick Zehner, Lisa
Shevenell, and Colin Williams
Great Basin Center for Geothermal Energy United
States Geological Survey
Funding U.S. Department of Energy, Assistant
Secretary Energy Efficiency and Renewable Energy
under DOE Golden Field Office Financial
Assistance Award DE-FG36-02ID14311
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• We are refining our models of undiscovered
  geothermal resources in the Great Basin and they
  continue to predict a significant number of
  undiscovered geothermal systems
• 2) A number of geothermal discoveries in the
  last few years provide corroboration that not
  only are there a large number of undiscovered
  systems, but that they can and will be found

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Most GIS-based Natural Resource Models predict
where conditions are favorable for the occurrence
of resources, but not how many undiscovered
resources remain Predicting undiscovered
resources is inherently more difficult and is
more like witchcraft and magic
The missing link involves defining where
resources have been adequately searched for
already, and where they havent been.
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To solve this problem, we have stepped outside
the geothermal arena to find a more general
mathematical approach for modeling undiscovered
natural resources (in process of being published
in Natural Resources Research).

x
Probability Model
Degree-of-Exploration Map
Undiscovered Resources
(1) AI AE AU (2) PIprior (NT unit cell) /
AI (3) PEprior (NT unit cell) / AE (4)
PEprior PIprior / ( AE/AI) (5) WIi,j ? ln
(Ni/NT) / (AIi/AI) j (6) WEi,j ? ln (Ni/NT) /
(AEi/AE) j (7) WEi,j ? ln (AIi/AI) /
(AEi/AE) x (Ni/Nt) / (AIi/AI) j (8) WEi,j ?
WIi,j ln (AE/AI) / (AEi/AIi)j (9) PU
PEpost (1 - fE)
Results estimated that 3.2 times more
undiscovered than known geothermal systems exist
in NV (geothermal systems defined as having
temperatures ? 100C)
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Favorable terrains defined using evidence
unaffected by groundwater


Geothermal Probability Model built using Weights
of Evidence
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Favorable terrains defined using evidence
unaffected by groundwater

6,600 wells

Geothermal Grad Wells
Water Table


160,000 wells
Degree-of-Exploration Map built using Fuzzy Logic
Carbonate aquifer
Other Wells
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Many options are available for building a
degree-of-exploration map
Variables used in this model - type of
wells - depth of wells - water
table depth - carbonate aquifer
Degree-of-Exploration Map
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Probability Model
Degree-of-Exploration Map
Undiscovered Resources
(1) AI AE AU (2) PIprior (NT unit cell) /
AI (3) PEprior (NT unit cell) / AE (4)
PEprior PIprior / ( AE/AI) (5) WIi,j ? ln
(Ni/NT) / (AIi/AI) j (6) WEi,j ? ln (Ni/NT) /
(AEi/AE) j (7) WEi,j ? ln (AIi/AI) /
(AEi/AE) x (Ni/Nt) / (AIi/AI) j (8) WEi,j ?
WIi,j ln (AE/AI) / (AEi/AIi)j (9) PU
PEpost (1 - fE)
Results estimated that 3.2 times more
undiscovered than known geothermal systems exist
in NV (geothermal systems defined as having
temperatures ? 100C)
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Recent discoveries of a number of previously
unknown geothermal systems in the Great Basin
suggest that a large undiscovered resource base
does in fact exist.
McGinness Hills Tungsten Mountain Astor
Pass Smoke Creek Desert Pyramid Rock Rhodes
Marsh Salt Wells north
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Newberry Crater
Geothermal Systems in Nevada Great Basin, USA
Big Southern Butte
China Hat
Borax Lake
Medicine Lake
McGinness Hills
Roosevelt/ Cove Fort
Mammoth
Current GB Geothermal Power Plant Capacity is
600 MWe
Coso
Boundary of Great Basin
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McGinness Hills (information generously provided
by NewCrest Resources and Tom Kilbey)
- exploration gold drilling to 1200 ft in 2004
steam encountered - 600 meter diameter
sinter terrace chalcedony and opal -
quartz-adularia veins beneath sinter dated at
3.2-2.2 Ma
There are additional occurrences of young
surficial opal and chalcedony in Nevada that have
not been drilled.
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Bedded sinter, McGinness Hills
Water samples yield geothermometers Drill-hole
25 214C Na-K-Ca-Mg 151C
quartz Drill-hole 26 209C Na-K-Ca-Mg
193C quartz analyzed in 2006 at NBMG
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Newberry Crater
Geothermal Systems in Nevada Great Basin, USA
Big Southern Butte
China Hat
Borax Lake
Medicine Lake
Tungsten Mountain
Roosevelt/ Cove Fort
Mammoth
Current GB Geothermal Power Plant Capacity is
600 MWe
Coso
Boundary of Great Basin
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Tungsten Mountain discovered during Au
exploration drilling in 2005,
2006 (information provided courtesy NewCrest
Resources, Tom Kilbey) - northwest side of
Edwards Creek Valley, Nevada - geothermal
system occupies possible step-over in range
bounding fault

• Most of 23 exploration holes hit hot water, with
• temperatures ranging from 50-95C, often with
  steam, at
• depths of 300-900 ft
• Hot water encountered over 2 km strike length,
  open in
• all directions

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Tungsten Mountain thermal area, looking
northeast across drilled area
Deep water from last hole drilled yielded
geothermometer temperature estimates Drill-hole
23 85C water at TD of 605 ft (180 m) 174C
Na-K-Ca-Mg 177C quartz analyzed in 2006 at DRI
Drill pad, hole 23
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Why was this area drilled? - small outcrop of
intense siliceous alteration along range
front - hydrothermal brecciation - anomalous
gold
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Other surface features - structurally
controlled tufa with vertical flow channels -
these same structures host chalcedony veins
Tufa
Discovery monument
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Newberry Crater
Geothermal Systems in Nevada Great Basin, USA
Big Southern Butte
China Hat
Borax Lake
Medicine Lake
Astor Pass
Roosevelt/ Cove Fort
Mammoth
Current GB Geothermal Power Plant Capacity is
600 MWe
Coso
Boundary of Great Basin
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Tufa tower near Astor Pass, Pyramid Lake Paiute
Reservation - near-boiling water (94C) at 200
ft depth beneath tower - other than the tufa,
there are no other surface geothermal
indicators - a strong shallow temperature
anomaly is present
Needle Rocks 6 km away
Discovered during reconnaissance geothermal
exploration - young northwest-striking
faults extending from Needle Rocks -
argillic alteration in adjacent Terraced Hills
- tufa tower
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Newberry Crater
Geothermal Systems in Nevada Great Basin, USA
Big Southern Butte
China Hat
Borax Lake
Medicine Lake
Smoke Creek Desert
Roosevelt/ Cove Fort
Mammoth
Current GB Geothermal Power Plant Capacity is
600 MWe
Coso
Boundary of Great Basin
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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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Newberry Crater
Geothermal Systems in Nevada Great Basin, USA
Big Southern Butte
China Hat
Borax Lake
Medicine Lake
Pyramid Rock
Roosevelt/ Cove Fort
Mammoth
Current GB Geothermal Power Plant Capacity is
600 MWe
Coso
Boundary of Great Basin
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Pyramid Lake Paiute Reservation
Pyramid Rock - boiling spring - 153C
geothermometers ( 15 miles from Needle Rocks)
There are other poorly documented occurrences of
hot water in the Great Basin that have not been
evaluated
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Newberry Crater
Geothermal Systems in Nevada Great Basin, USA
Big Southern Butte
China Hat
Borax Lake
Medicine Lake
Roosevelt/ Cove Fort
Rhodes Marsh
Mammoth
Current GB Geothermal Power Plant Capacity is
600 MWe
Coso
Boundary of Great Basin
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Rhodes Marsh, Mineral County, NV. Red
strike slip fault Black normal fault
Soda Springs, 112 geotherm.
X
Well, 146 / 148 geotherm. 1,830 ppm SO4,
sampled 1959
Active range front faulting
opalized sands
springs/wells
Warm well with borates 155 / 162 geotherm. 361
ppm Cl, 414 ppm SO4 sampled 2005
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The range front east of Rhodes Marsh is a site of
active faulting with apparently complex fault
geometries.
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Rhodes Marsh, Nevada
Opalized sands are exposed in small windows in
the piedmont colluvium over a distance of gt 2,000
ft
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Newberry Crater
Geothermal Systems in Nevada Great Basin, USA
Big Southern Butte
China Hat
Borax Lake
Medicine Lake
Roosevelt/ Cove Fort
Salt Wells
Mammoth
Current GB Geothermal Power Plant Capacity is
600 MWe
Coso
Boundary of Great Basin
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Detailed mapping of surface geothermal features
at Salt Wells has 1) identified faults that
control geothermal fluid flow over a
distance of 9 kms 2) increased awareness of a
possible second upwelling zone on the north
end 3) identified surface and near- surface
hot waters on the north end that can be
sampled for geochemical analysis
North End
South End (power plant under construction)
1 km
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• OTHER RECENT DEVELOPMENTS
• Blue Mountain high measured and calculated
  temperatures
• (gt160C and gt200C respectively)
• 2) Fallon Navy Air Base measured/inferred water

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CONCLUSIONS
ARGUMENTS OF THIS TALK
1) Undiscovered geothermal systems really do
exist in the Great Basin WHY? -
blind targets (similar to gold exploration) -
barriers to exploration (economics and
leasing) - temperature gradients dont solve
everything 2) These undiscovered systems are
findable
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The End