preliminary results for a near surface 3d seismic survey ... · geothermal energy •the united...
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Andrew Lamb1, Kasper van Wijk1, Lee Liberty1 , Mike Batzle2, André Revil2, Kyle Richards2 and
Chuck Diggins3
1 Department of Geosciences, Boise State University, Boise, ID
2 Department of Geophysics, Colorado School of Mines, Golden, CO3 Fusion Petroleum Technologies, Inc., Boulder, CO
Preliminary results for a near surface 3D
seismic survey of a geothermal system in
Colorado
Overview
•Geophysics Field Camp
•Geothermal Energy in the US
•Hypotheses
•Study Area and Geological Setting
•Self Potential Survey
•3-D High Resolution Seismic Survey
•Conclusions
•Future Work
Field Camp 2007 - 2010
•Four years of Joint Geophysics Field Camp• Colorado School of Mines
• Boise State University
• Imperial College London
•Geophysical Methods Used• Deep and shallow reflection seismic
• Electrical resistivity
• Electro-magnetics
• Self potential
• Magnetics
• Gravity
• Passive seismology
• Well logging and VSP
Geothermal Energy
•The United States leads the world in geothermal electricity
production with 3,086 MW of installed capacity from 77 power
plants.
•Current development will increase this to almost 4,000 MW.
•This represents over 30% of world online capacity and meets the
energy needs of approximately 4 million homes.
•Geothermal is estimated to cost 3.6 cents per kilowatt-hour, versus
5.5 cents per kilowatt-hour for coal (Mims, 2009).
•Colorado has a target of 30% renewable energy by 2020 (Minard,
2010).
US Heat Flow Map
Source: SMU Geothermal Lab (http://smu.edu/geothermal/heatflow/heatflow.htm)
Colorado Heat Flow Map
Modified from Colorado Geological Survey, 2010
Hypotheses
•Explore new joint inversion techniques to image subsurface
structure, fractures, faults and fluid temperatures in the Mt.
Princeton shallow geothermal system.
•Explore the possibilities of geothermal power generation in the
Upper Arkansas Valley.
•Reduce exploration risk (1 in 10 success)
Study Area and Geological Setting
Upper Arkansas Valley
Salida
Mt. Princeton
Buena VistaModified from Richards et al., 2010
Rio Grand Rift
Upper Arkansas Valley
Salida
Mt. Princeton
Buena VistaModified from Richards et al., 2010
Rio Grand Rift
Upper Arkansas Valley
Modified from Richards et al., 2010
Heat Source
Upper Arkansas Valley
Salida
Mt. Princeton
Buena Vista
Modified from Richards et al., 2010
Upper Arkansas Valley
Salida
Mt. Princeton
Buena Vista
Modified from Richards et al., 2010
Geothermal Springs
-Why these locations?
Upper Arkansas Valley
Salida
Mt. Princeton
Buena Vista
Sawatch Fault
Modified from Richards et al., 2010
Upper Arkansas Valley
Salida
Mt. Princeton
Buena Vista
Sawatch Fault
Modified from Richards et al., 2010
Upper Arkansas Valley
Salida
Mt. Princeton
Buena Vista
Sawatch Fault
Modified from Richards et al., 2010
Chalk Creek Valley
Chalk Creek Valley
Mt. Princeton
From:
Richards et al. 2010
Chalk Creek Valley
Mt. Princeton
From:
Richards et al. 2010
Mt. Princeton Study Site
Mt. Princeton Study Site
Mt. Princeton
Hot Springs
Resort
Elevation Increase
[200m N = +20m]
Mt. Princeton
The Self Potential Method
OH 2+
O-
O-
O-
OH
OH
+ Na
+
Cl-
O -
O-
Na
+ Na
+ Na
+ Na
+ Na
Cl-
+ Na
EAU LIBRE
Cl-
+ Na
H O2
+
O-
HO
HO
O-
O-
O-
O-
+ Na
COUCHEDE
STERN+ Na
COUCHEDIFFUSE
Cl-
+ Na
+ Na
+ Na
+ Na
Plan d
d
VITESSE DU FLUIDE
+ Na
Cl-
MINERAUX
Velocity of the fluid
SternLayer
Diffuselayer
Free water
Ground water flow is responsible for
an electrical field
Mineral grains
The Self Potential Method
Self Potential Acquisition•Self potential and electrical resistivity studies in the 2008 field
camp showed evidence for upwelling of hot water
Interpretation•East-West fracture with upwelling hot water anomalies
•Wells to north and south of fracture have cold & hot water respectively.
3-D High Resolution Seismic Survey
•A 3-D high-resolution seismic survey was conducted during the
2009 field camp with the following acquisition parameters:• Footprint of survey was approximately 240 m x 240 m
• Source was an Industrial Vehicles Minivib Model T-15000
• Total of ~400 shots into a 576 channel Geode recording system
3-D Survey Design
• 40 Hz vertical phones
• 5 m inline receiver int.
• 20 m xline receiver int.
• 10 m inline source int.
• 20 m xline source int.
• 576 channels
• 1 ms sampling
3-D Seismic Survey Results
•Review shot records and first arrival events
•Two layer refraction model
•Refraction tomography
•Preliminary reflection stack
Shot Records (North to South)
Synthetic Shot Record (North) Field Shot Record
Shot Records (South to North)
Synthetic Shot Record Field Shot Record
First Arrivals
First Arrivals
First Arrivals
First Arrivals
Two Layer Refraction Model
Two Layer Refraction Model
Sediments
Bedrock
Sediments
Bedrock
Tomography: Bedrock ElevationAssume Bedrock Velocity ~ 3300 m/s
Self Potential with Bedrock ContoursAssume Bedrock Velocity ~ 3300 m/s
Self Potential with Bedrock ContoursAssume Bedrock Velocity ~ 3300 m/s
Conclusions
•Bedrock low trends from west-southwest to east-northeast.
•The bedrock low may have been formed by glacial scouring or is an old river channel.
•SP upwelling events are located along the bedrock low.
•The low refraction velocities suggest the granite is heavily fractured and most likely hydrothermally altered.