Our Evolving Knowledge of Nevadas Geothermal Resource Potential

1
www.unr.edu/geothermal
Our Evolving Knowledge of Nevadas Geothermal
Resource Potential Lisa Shevenell, Mark
Coolbaugh, Chris Sladek, Rick Zehner, Chris
Kratt Geothermal Resources Council October 8,
2008
2
Long known that there are many geothermal
features in Nevada From ?2700 digitized springs
from 7.5 Quads chemistry and temperature of
1030 thermal springs is unknown
Shevenell, Garside
3
(No Transcript)
4
Assessment for Nevada

• GRC Bull, June 2008 (Shevenell, Morris,
  Blackwell)
• Preferred values _at_ known systems
• Permits
• Heat Loss
• GeothermEx PIER
• WGA
• Nominal 5 MW assumption
• Minimum 2170 MW _at_ 160 sites

5
New Exploration and Assessment Methods at the

• Conducting regional studies to develop models and
  build geothermal potential maps local studies to
  better understand systems

6
Gravity, Dilation, T-grad, Seismicity
Coolbaugh, et al.
7
Detailed Mapping in Modern Plate Tectonic Context
Desert Peak
Overlapping Normal Faults

• En echelon NNE normal faults
• Subvertical conduits
• High fracture density
• Multiple step overs
• Other favorable settings
• Terminations of range-front faults (Gerlach)
• Intermeshing opposing systems (Salt Wells)

Faulds
8

• We also 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 provides corroboration that not
  only are there a large number of undiscovered
  systems, but that they can and will be found

9
Preliminary example of how to model the location
of undiscovered geothermal resources in
Nevada Although the results were encouraging,
the methodology was qualitative. Published
scientific methodology for linking degree of
exploration with occurrence models is lacking.
Coolbaugh, Shevenell
10
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
11
Many High-Temperature (undiscovered) geothermal
systems in Great Basin are blind at the surface
(no hot springs)
Low water tables, near-surface impermeable cap
rocks, and laterally flowing groundwater in
aquifers can prevent hot springs from forming at
the surface
Hot Springs Mountains near Desert Peak, NV
Elevation ranges from 1200 m to 2200 m (900 m
maximum relief)
12
Silicified sediments (opal)
All blind geothermal systems in Nevada that
are currently producing electricity have some
surface signatures
Carbonate tufa/travertine
Clay alteration
Borate and sulfate evaporites
13

• Sites Recently Discovered
• Gold Exploration
• T-Surveys
• Borates
• Cold Spr. Chem.

14
Remote Sensing for mapping mineralogy and thermal
anomalies
Hymap 3-5 meter
Kratt, Calvin
15
ASTER delineates borates in SW Nevada

• locate systems without hot springs issuing at
  surface

ASTER color Composite image
Kratt, Coolbaugh
16
Rhodes Marsh, Mineral County, NV. Red
strike slip fault Black normal fault
Soda Springs, 112 geotherm.
X
Active range front faulting
opalized sands
springs/wells
Warm well with borates 155 / 162
geotherm. sampled 2005
Coolbaugh, Kratt, Zehner, Sladek
17
New Assessment Methods Proof of concept Shallow
Temperature Surveys
Sladek, Zehner, Kratt, Coolbaugh, Penfield
18
Thermal gradient wells Desert Queen (few,
expensive, generalized anomaly)
19
Shallow probes (many, inexpensive, more detail)
Sladek, Coolbaugh
20
New Discoveries

• Astor Pass RS, TS
• Blue Mountain GE
• Bonham Ranch RS, TS
• McGinness Hills GE
• Rhodes Marsh RS, TS
• Salt Wells (better defined) TS
• Teels Marsh RS, TS
• Tungsten Mountain GE, TS

GE Gold Exploration RS Remote Sensing
TS Temperature Surveys
21
Teels Marsh
Evaporites all have similar appearance
Ideal for identification with satellite data
ASTER Satellite

• Covers 60 by 60 km
• 3 visible bands and 6 short-wave infrared bands
  (0.45 2.6 µm)
• visible and short-wave band combined to achieve
  30m spatial resolution

22
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

• All 23 exploration holes hit hot water, with
• temperatures ranging from 50-95C, often with
  steam, at
• depths of 90-275 m
• Hot water encountered over 2 km strike length,
  open in
• all directions
• - Geothermometers 174C Na-K-Ca-Mg 177C quartz

23
Kratt, Zehner, Penfield
24
Teels Marsh December 2007
Kratt, Zehner, Penfield
25
Temperatures (C) From Cold Springs
26
Fernley
Hot well, 60C at depth, 32C in storage
tank 149C qtz 149C Na-K-Ca-Mg geothermometers
Warm well, 29C in storage tank 145C qtz 132C
Na-K-Ca-Mg geothermometers
Junction of major Walker Lane structural elements
34.0C warm spring
Lahontan Reservoir
Silver Springs
27
Conclusions

• Research has enabled the development of
  significant new evaluation and exploration tools
• New tools helping to identify new geothermal
  resources and better assess existing ones
• Undiscovered resource base in the GB is
  significant but unknown need assessment
• Geothermal energy has the potential to be a major
  contributor to renewable energy portfolios in NV

28
(No Transcript)
29
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
30
Other Methods to Find Blind Systems

• 2 m hole was dug into a playa Ex.
• Salt Wells
• Water temperature 84.8ºC
• Geothermometer temperature 192ºC
• Shallow Temperature surveys

Cold Sites

• Cold springs/wells lt 20ºC in four known
  geothermal areas show anomalous geothermal
  temperatures (121º - 142º).
• More located not yet drilled to verify

Shevenell, Garside, Sladek, Coolbaugh, Penfield
31
Kratt, Calvin
32
(No Transcript)