EXPLORATION TECHNOLOGIES
WORKSHOP
Introduction & Brief
Classification of Geothermal
Resources
GRC Annual Meeting 2006
San Diego, California
Paul Brophy, EGS Inc.
Workshop Agenda
► Session
1
- Exploration Methods
► Session
2. - Exploration Case Histories
►Coso
►Roosevelt
►Karaha
► Session
Bodas (Indonesia)
3. - Panel Discussion
►What
Works- What doesn’t Work
Exploration Settings
Type A - Magma-heated, dry steam resources
(The Geysers)
Type B - Andesitic volcanic resources
(Philippines, Indonesia, Central &
South America)
Type C - Caldera resources
( Medicine Lake, Valles Caldera, Los
Humeros, Yellowstone)
Type D - Sedimentary–hosted, volcanic-related
resources (Imperial Valley)
Type E - Extensional tectonic, fault-controlled
resources (Great Basin)
Type F - Oceanic-ridge, basaltic resources
( Hawaii, Iceland, Azores)
Type A
Magma-related, Dry Steam Resources
(Example – The Geysers, CA)
Type A - Magma-related, Dry Steam
Resources

Topography:
Rugged? mountainous?

Climate:
Variable?

Depth to Resource:
meters)
Usually deep ( 2500 – 4000

Surface Manifestations:
Restricted

Permeability:
Low to moderate fracture
permeability

Environmental/Political: None
Type B Andesitic - Volcanic Resources
(Example – Systems of the Circum-Pacific)
Type B – Andesitic-Volcanic
Resources

Topography:
Usually mountainous

Climate:
precipitation
Variable – usually high

Depth to Resource:
Deep to moderate

Surface Manifestations:
Restricted – depending on depth
and shallow ground water

Permeability:
Low to moderate fracture
permeability – often highly
variable

Environmental/Political: Some countries with political
unrest
Type C - Caldera Resources
(Example – Medicine Lake, CA)
Type C – Caldera Resources

Topography:
caldera
Ring fractures often rugged,
floor gentle topgraphy

Climate:
Variable?

Depth to Resource:
meters)
Moderate to shallow (- 2500

Surface Manifestations:
Common

Permeability:
Low fracture permeability – often
with thick tuff units

Environmental/Political: Often very scenic –
environmentally
sensitive
Type D – Sedimentary-hosted,
Volcanic Resources
(Example – East Mesa, CA, Cerro Prieto, Mexico)
Type D – Sedimentary-hosted,
Volcanic Resources

Topography:
relief
Usually low topographic

Climate:
Arid, low precipitation

Depth to Resource:
Intermediate ( 2000 – 3500
meters)

Surface Manifestations:

Permeability:

Environmental/Political:
Very restricted
Variable?
Usually limited?
Type E – Extensional, Fault-controlled, Resources
(Examples – Dixie Valley, Desert Peak)
Type E – Extensional, Faultcontrolled
Resources

Topography:
Rugged on upthrow, low on valley
floor

Climate:
Usually dry with low precipitation

Depth to Resource:
meters)
Usually deep ( 2500 – 3500

Surface Manifestations:
Usually restricted to fault traces

Permeability:
Donimantly fault controlled

Environmental/Political: None
Type F - Oceanic, Basalt-hosted Resources
(Example – Puna, Hawaii)
Type F – Oceanic, Basalt-hosted
Resources

Topography:
Rugged to flat?

Climate:
Islands – high precipitation

Depth to Resource:
Shallow ( 1000 – 2000 meters)

Surface Manifestations:
Common

Permeability:
High horizontal permeability,
variable vertical permeability

Environmental/Political: Environmental sensitive