A Case Study of the Roosevelt Hot
Springs Geothermal Field, Utah
Joe Moore
Energy & Geoscience Institute
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Outline of Case Study
• Regional Geologic Setting
• Overview of early history and development
• Results of geologic, geochemical and
geophysical exploration studies
• Evaluation of the data for exploration
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Location of
Roosevelt Hot
Springs (RV)
Cyan: > 3.0 Ra
Yellow: 2 – 3 Ra
Red : 1 – 2 Ra
Orange: 0.6 – 1 Ra
Green: 0. 3 – 0. 6 Ra
Blue: < 0.3 Ra
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HEAT SOURCE
Circles and Squares: Magmatic
Triangles: Extensional
Diamonds: not sure
Mantle Helium Evidence
(Kennedy and van Soest, 2005)
CHS
Quaternary
Volcanic
Activity
Geothermal Systems
CF-S: Cove Fort-Sulphurdale
CHS: Crater Hot Springs
RHS: Roosevelt Hot Springs
T: Thermo
CF-S
RHS
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T
QR
Pink: Mountain Ranges
Purple: Dominantly basalt
QR: Quaternary rhyolite
Aerial View of Roosevelt Hot Springs Geothermal Field
RHS
Negro Mag
Fault (E-W)
Opal Mound
Rhyolite
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Opal Mound
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View of Mineral Mountains
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View Looking to the West
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Early History and Development
(exerpted from R. Forrest, GRC Guidebook 7, 1980)
• 1880’s: hot springs were discovered and named McKeans
• 1900’s: a resort was established (operated by Negro Mag)
• 1908: Lee identifed water type as Na-SO4-Cl with flows of 10
gpm at 190oF
• 1950: flow decreased to 1 gpm; temperature to 185oF
• 1966: Mundorff (1970) reported flows had ceased
• 1967: McDonald and Davie drill 80 ft well at the Opal Mound 4
km south of the old resort and encountered boiling water. A
second hole was drilled to 165 ft and encountered water that
flashed to steam. Well plugged and reentered in 1968. Drilled
to 270 ft, encountered water at 270oF; after 2 months plugged
and abandoned.
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Early History and Development (cont.)
• 1968-1971: MaDonald applied for geothermal rights and mineral
leases; designated a KGRA in 1971.
• 1972: Thermal Power Company formed by Davie. Scientific
studies at the U. of Utah initiated (most published 1975-early
80s)
• 1973: Temperature gradient wells drilled.
• 1974: Competitive lease sale. Phillips Petroleum Company
obtains 18871 acres
• 1975-1979: Productive wells are drilled near the Opal Mound
and old resort in 1976 and flow testing begins. Production
wells range from 1200-7300 ft depth with T max. of 268oC.
Phillips, Thermal Power, O’Brian, Amax agree to develop field
With Phillips Petroleum as operator. 6 of the 11 wells in the unit
are commercial. Geoscientific data are placed in the public
domain (1977-1979) through the US Dept. of Energy’s Industry
Coupled Program. Production estimated at 120 MWe.
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Early History and Development (cont.)
• 1980: Phillips Petroleum and Utah Power and Light enter
negotiations to develop field.
• 1981: 1.6 MWe turbine installed and tested.
• 1984: Full production begins with a 23.5 MW (26 Mw gross)
plant.
• 2007: A bottoming cycle will be added, providing an additional
11 MWe
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Geological Methods
• Photogeology (low sun angle, b/w, high sun angle, stereo
color, multispectral infrared)
• Reconnaissance mapping
• Structural mapping
• Volcanic stratigraphy, paelomagnetism, magma
thermodynamic modeling
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Geochemical Methods
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Analysis of surficial deposits
Analysis of subsurface alteration
Chemical and Isotopic analyses of waters
Trace element surveys of soils and well samples
Gamma-ray spectrometry
Assessment of exothermic reactions to heat flow
Geothermometry and analysis of water-rock interactions
Chemistry of volcanic rocks
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Geophysical Methods
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Gravity survey
Precise leveling
Magnetic survey
Aeromagnetic survey
Resistivity (Schlumberger, Dipole-dipole) surveys
Induced polarization survey
Mise-a-la-masse resistivity surveys
AMT/MT survey
Electromagnetic sounding
Self-potential orientation surveys
Earthquake monitoring
Refraction seismic survey
Thermal gradients and heat flow
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Geologic Studies: Lineament Map
P = Photo interpretation
G = Geologic observation
R = Resistivity survey
M = Aeromagnetic survey
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(Ward et al., 1978)
Reconnaissance
Mapping
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(Ward et al., 1978)
Bailey Ridge Rhyolite Flow
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Ts/Tpg
Detailed
Structural Map
PCg
PCbg
Trf
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Sibbett and Nielson (1980)
Highly Fractured Granitic Rocks
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Comparison of
Geologic Cross
Sections Based
on
Reconnaissance
and Detailed
Mapping
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Regional Groundwater Geochemistry
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Fluid Chemistry
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Percent
Groundwater
Mixing
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(Capuano and Cole, 1982)
Trace Element Distributions
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Hg
Concentrations
at Depth
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Terrain
Corrected
Bouguer
Gravity Map
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(Carter and Cook, 1978)
Gravity Model
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(Ward et al., 1978)
Density contrast 0.5
g/cm3
Total
Aeromagnetic
Intensity Residual
Map
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(Ward et al., 1978)
Earthquake
Epicenter
Locations
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(Ward et al., 1978)
Structural Interpretation of Vibroseis
Profile
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(Ross et al., 1982)
Dipole-Dipole
Survey:
Interpreted
Resistivity
Sections
Depth interval:
100-150 m
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(Ross et al., 1982)
Magnetotelluric Profile
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(Wannamaker et al., 1980)
Heat Flow Map
(mW/m2)
Thermal characteristics based on
measurements in 53 wells
Most less than 110 m
Gradients range from 6 to 3330oC/km
(Great Basin average 35-40C/km)
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(Wilson and Chapman, 1980)
Conclusions
• A very suite of geologic, geochemical and
geophysical measurements were collected at
Roosevelt Hot Springs during the 1970s and
1980s.
• The Opal Mound Fault appears to form the
western boundary of the productive
reservoir.
• Aeromagnetic and seismic reflection and
refraction surveys were of little using in
delineating the prospect.
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Conclusions
• MT investigations hold significant promise
but interpretational problems have to be
overcome.
• Studies of particular value include:
– Detailed structural mapping
– Geochemical interpretations
– Thermal gradient measurement (100-200 m
holes)
– Dipole-dipole surveys
– Alteration studies of cores and cuttings
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