volcanic features and geothermal potential · 2017-05-05 · volcanic features and geothermal...
TRANSCRIPT
Based on work by:
Pete Stelling, Nick Hinz, Lisa Shevenell, Mark Coolbaugh, Glenn Melosh, William Cumming
Volcanic Features and Geothermal Potential
Miravalles V geothermal plant and volcano, Costa Rica (Think GeoEnergy, Ormat)
Testing Correlations Between Volcanic Features and Geothermal Productivity
Inventoried volcanic characteristics of nearest volcanic system to every geothermal system
hosted by subduction zone volcanoes
Data sources include Google Earth, Smithsonian, Volcano Observatories, NGDS,
igneous geochemistry database;
Compiled geothermal production database
Testing Correlations: Limitations
Only positive case studies
(no failed exploration data)
Uniformity of dataset omits specific details
(general trends, many exceptions)
Many data not public
Small statistical populations (85 power plants on 74 volcanoes)
Testing Correlations Between Volcanic Features and Geothermal Productivity
Anecdotal Correlations Tested
• Larger volcanoes support larger hydrothermal systems
• Rhyolite domes correlate with larger, hotter systems
• More flank vents promote larger hydrothermal system
• Recent volcanic activity promotes geothermal system development
Common anecdotal correlations
• Larger hydrothermal systems on larger volcanoes
– Longer-lived magmatic systems, greater heat flow, geothermal system development
Mayon Volcano, Philippines (Wikipedia)
0
50
100
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300
350
0 100 200 300 400 500
Inst
alle
d P
ow
er
(MW
e)
Caldera Area (km2)
CalderasHolocene caldera area Pleistocene caldera area
Whakamaru(1600 km2, 795 MWe)
0
100
200
300
400
500
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700
800
900
0 100 200 300 400 500
Stratocone footprint (km2)
Stratocones
Holocene Stratocone area Pleistocene Stratocone Area
Size of Volcanic Features
No obvious correlation observed
n=33 n=67
Common anecdotal correlations
• Rhyolite domes positive indicator of geothermal potential
– Silicic volcanic systems
Inyo Domes, Long Valley, CA
Flank Vents and Installed Power
0
50
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0 10 20 30 40 50 60
Cumulative Dome Area (km2)
Holocene dome area Pleistocene dome area
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450
500
0 5 10 15 20 25 30
Inst
alle
d P
ow
er
(MW
e)
Number of Flank Vents
# Cinder Cones # Domes
Little correlation
Flank vent composition difficult to determine
n=47 n=48
Eruptive Composition
0.0
100.0
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400.0
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700.0
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900.0
0 1 2 3 4 5
Eruptive Diversity
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900.0
0.00 1.00 2.00 3.00 4.00 5.00
Average Composition
bas and dac rhy
0=no data, 1=basalt, 2=andesite, 3=dacite, 4=rhyolite, 5=phreatic
up to 4 different rock types
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Most Recent Eruptive Product
bas and dac rhy phr
Data from GeoROC database (http://georoc.mpch-mainz.gwdg.de/georoc/)
Anecdotal evidence suggested rhyolite is a positive indicator of geothermal potential
Common anecdotal correlations
• Eruptive frequency
– Frequently active systems have higher heat flow
USGS
Common anecdotal correlations • Eruptive frequency
– No obvious correlation (basaltic systems more active)
0
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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Inst
alle
d P
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(MW
e)
Eruptions per 100 years
Basalt
andesite
dacite
rhyolite
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0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Inst
alle
d P
ow
er
(MW
e)
Eruptions per 100 years
Basalt
andesite
dacite
rhyolite
Common anecdotal correlations
• Years since last eruption
– More recently active systems have higher heat flow
Momotombo Volcano and geothermal power plant, Nicaragua (www.indicepr.com)
Years Since Last Eruption
0
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0 1000 2000 3000 4000 5000
Inst
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d P
ow
er
(MW
e)
Years Since Last Eruption
n = 32
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0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000
Inst
alle
d P
ow
er
(MW
e)
Years Since Last Eruption
25% systems
35% power
19% systems
45% power
40% systems
18% power
16% systems
4% power
Years Since Last Eruption
15%
36%
46%46%
48% 48%
54%
65%66% 68%
68% 69%
91%97%
98% 98%
32%
51% 84%89% 95%
-200
800
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2800
3800
4800
5800
6800
7800
0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000
Cu
mu
lati
ve In
stal
led
Po
we
r (M
We
)
Years since last eruption
Total cumulative power (n=48)
Mafic VC (basaltic+andesitic; n=34)
Felsic VC (dacitic+rhyolitic; n=10)
Total Installed Power (all VC)
Common anecdotal correlations
• Presence of Calderas
– Larger volcanic systems, more permeability
Krafla caldera and geothermal power plant, Iceland (volcano.si.edu)
Caldera Presence, Age
Pleistocene 19 systems;
2793 MWe total (36%)
140 MWe avg
Holocene
24 systems;
1455 MWe total (19%)
61 MWe avg Non-calderasystems
32 systems; 3584 MWe total
(43%)
108 MWe avg.
0
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45
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Power with caldera Power without caldera
# vo
lcan
ic c
ente
rs
Fumaroles and Installed Power
La Labor fumarole field, Apaneca Range, El Salvador (hosting Ahuachapan geothermal system
Production correlates with fumarole area
Fumaroles and Installed Power
Fumarole field size (m2) and well geothermometer results (oC)
Unknown 100-150 150-200 200-250 250-300 >300
Fumarole Area (m2) Mean MW
>100,000 - 300,000 2 174 437 224
>30,000 - 100,000 15 264 102 123
10,000 -30,000 80 38 81
<10,000 61 180 242 112
Y-Unk Area 0
N 0
Unknown 59 36 76 45
0% 0% 0% 8% 42% 51%
Mean MW 0 0 2 53 128 167
Mean MWe/System
93% of commercial-grade geothermal systems in arcs have flank fumaroles
Production correlates with fumarole area
Significant Conclusions from Volcanic Inventory
• Strong correlation between fumaroles and geothermal
• Very few statistically significant correlations between volcanic attributes and installed power– Interpretation: Heat source in arcs not a problem, esp. for <100
MWe systems
• Few traditional geothermal indicators show correlation– Presence and abundance of domes, flank vents
– Edifice size
– Composition (dataset is less reliable)
• Possible correlation between installed power and older calderas, younger eruptions and composition
Questions?
Mt. Bromo, Indonesia
Proximity to VC
0.1
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1000.0
0 10 20 30 40 50 60 70 80
Inst
alle
d M
eg
awat
ts
Distance from Volcanic Center
Installed Power vs. Distance from VC
0-1 km
1-8 km
8-20 km
20-80 km
48% systems47% power
19% systems10% power
10% systems23% power
24% systems20% power
Momotombo, Nicaragua; D=3.1 km
Muaralabuh, Sumatra; D=16.8 km
Direct Evidence Inventory:Maximum temperatures