Overview of Indonesian Geothermal System
The Resources Beyond High Enthalpy
Magmatic/Volcanic Systems
By
Dr.Eng. Suryantini
ITB
4/3/2017
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Outline
• Current Condition of Indonesian Geothermal
Resources and its Systems
• Geology of Geothermal Systems
• Resources Beyond High Enthalpy
Volcanic/Magmatic Associated Geothermal
Systems
• Concluding Remark - The Future of Exploration,
Utilization Challenges and Opportunities
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Current Condition of
Indonesian Geothermal Resources and its Systems
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Current Condition of
Indonesian Geothermal Resources
Sources : MEMR, 2016
GWA Producer
GWA Un-Producer
GWA in bidding
Prospects  69 (<21%) Geothermal Working Areas (GWA)
 11 Production GWA (<16% from total GWA or 3% from total prospects)
29,452 MW Potential  2,288 Mwe (7.8%) Proven Reserve
 1,438.5 Mwe (63% from Proven or <5% from total potential) Production
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Indonesian Geothermal vs Present Day Volcanic Arc
Sources : MEMR, 2016
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Most of the Prospects are associated with volcanic arc
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Tectonic that control volcanoes and geothermal occurrences
•
Most geothermal occurrences is associated with volcanic or magmatic heat sources
Other is non-volcanic or amagmatic heat source  extinct magmatic at old subduction
zone, tectonic extensional domain, or Intra-cratonic basin, or conductive system 6
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Current Condition of Indonesian Geothermal Resources and its Systems
1)
Imbalance between resource availability and development  Inefficient
geothermal energy utilization
2)
Geosciences perspective on this condition i.e.
a. The prospect is less attractive due to i.e. low potential,  unsuitable for world
class developer
b. Lack of understanding about geothermal system  improper project plan 
suspend of the project
c. Misunderstanding of reservoir permeability as drilling target  drilling failure 
suspend of the project
3)
Most of geothermal systems that produce electricity is associated with
volcanic or magmatic heat source with prominent surface manifestation 
what if the manifestation is very little and less or inactive?
What if the volcanism is absence?
4)
Low-Medium Enthalpy has not been explored or studied further
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Geology of Geothermal Systems
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• “A geothermal system is any localized geologic setting where
portions of the Earth‫׳‬s thermal energy may be extracted from
natural or artificially induced circulating fluids transported to a
point of use.” (Moeck, 2014)
• Geologic setting has a fundamental influence on the potential
temperature, on the fluid composition, the reservoir
characteristics and mode of heat transfer (convective or
conductive)
• Failure in understanding this geologic setting (and all the
supporting geologic elements that determine the setting) may
cause many technical and financial problems that eventually
leads to projects suspended or terminated.
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Geothermal Plays – IGA classification
• “Geothermal Play” is adopted from Petroleum
• Translated to geothermal systems, a geothermal play
type might be defined as a geological setting that
includes
a heat source,
heat migration pathway,
heat/fluid storage capacity,
and the potential for economic recovery of the heat
(IGA, 2014)
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(IGA, 2014)
Indonesian geothermal systems have all possible play types
Which play type is your geothermal system?
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Depth (km)
Magmatic Play Type – Active or Recent Magma Intrusion
Age of Volcanism
(IGA, 2014)
- Active magmatism: volcanism <500 yrs
- Recent magmatism: volcanism 500-50,000 yrs
- Inactive or extinct magmatism: volcanism >50,000 yrs
• A familiar model for Indonesian Geothermal System.
• Recent (but not active) intrusions underneath or in the vicinity of volcanoes
heat sources, with intensive surface manifestation.
• 4/3/2017
An active magma chamber does not always produce volcanism !
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Depth (km)
Active or recent magmatic play type with intrusive magma chamber.
Magma chamber
Pluton
(IGA, 2014)
• Influenced by active faulting, deep rooted magmas can intrude beneath
flat terrain with no volcanism.
• Manifestation might be occur
• An upflow and outflow zone might be occur provided the topography of
volcano support this
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Extinct magmatic play types controlled by late Cenozoic to
Quaternary plutons or batholiths without associated volcanism.
In Lardarelo:
Depth (km)
Pliocent Epoch
- At 1.3-3.8 Ma.
- Extensional event
-Granite intrusion
-Low-angle normal
faults recharge
Metasediments
(IGA, 2014)
Quartenary granitic pluton
Pleistocene Epoch
-At 0.2-0.3 Ma
-magmatic event
primary heat source
• Examples are Lardarelo and The Geyser
• Typically located along continent-continent convergent or transform margins
with recent magmatism
• Surrounding mountain ranges provide high recharge rates of meteoric water
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• 4/3/2017
Manifestation might be occur
Extinct magmatic play types controlled by late Cenozoic to
Quaternary plutons or batholiths with associated volcanism.
(IGA, 2014)
• Previous play type can coexist with active or recent volcanism
• Hence two systems might be coexist
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Which one is your systems ?
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Extensional domain play type, with possible fault
controlled fluid flow paths.
(IGA, 2014)
• The elevated mantle  principal heat source  high thermal gradient
• deep faults or permeable formations  fluid circulation path
• Non-magmatic, may be “fault zone controlled” or “fault-leakage controlled”
at the system scale.
• Segmented faults are more favorable for geothermal systems than large
faults with large offsets
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Conduction-Dominated Play Types
• Passive geothermal systems  absence of fast convective or fluids
dynamics
• Passive tectonic plate settings  no significant recent tectonism or
magmatism.
• Favorable geologic setting : extensional, divergent margins and
grabens, or lithospheric subsidence basins, foreland basins within
orogenic belts, and crystalline basement underlying thermally
insulating sediments,
• Classified based on natural porosity–permeability ratio within the
potential reservoir rock, and the absence or presence of producible
natural reservoir fluids.
Intracratonic Basin Type,
Orogenic Belt Type, and
Basement Type
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Conduction-Dominated Play Types
Intracratonic Basin Type
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Orogenic Belt Type
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Resources Beyond High Enthalpy Volcanic/Magmatic
Associated Geothermal Systems
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Key point of volcanic or magmatic geothermal system
1. Age of volcanism determine the maturity of volcanism
 radiometric age dating ?
2. An active magma chamber does not always produce
volcanism  geophysics ?
3. Intrusion not beneath the system but in the vicinity,
what if composite volcano? Or caldera?  geophysics ?
4. Most of geothermal exploration is guided by the
occurrence of manifestation, in absence of surface
manifestation or when the upflow-outflow zone is
subtle  Exploration concept play significant roles
5. An insight into the whole model or concept is necessary
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Tangkuban Perahu
Is Ciater part of Tangkuban Perahu System?
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Patuha
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Wayang Windu, Darajat and Kamojang
Is there any geothermal system between Darajat-Kamojang?
Is there any potential at Malabar north of Wayang Windu?
Kamojang
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Wayang
Windu
Darajat
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Silangkitang - Sarula
Namora
Silangkitang
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Muaralaboh
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Integrating regional data from petroleum exploration
Would
it be possible to find Extensional domain play type
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Integrating with regional data from petroleum
exploration : Lesson Learned
Geothermal System in Sumatra is controlled by
volcanism due to subduction and mega strike slip
Great Sumatran Fault which lies on continental
granitic basement. It is a unique complexes system.
Understanding the tectonic, geology and play type is
crucial for discovery of geothermal system.
Try to elaborate all geological data even from
petroleum exploration or other survey
Discuss the data, share the knowledge
Blind system may be discovered
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Discuss the data, share the knowledge to get
the complete picture
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What about geothermal system in Sulawesi and
others in eastern Indonesia?
Hall and
Wilson, 2000
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Conduction dominated in sedimentary basin
Geothermal Potential at the Sedimentary Basin in Sumatera
Utilization of abandoned petroleum well (~700 abandoned well in Sumatera only)
Regional Heat flow map is necessary
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There
are >60 Tertiary Sedimentary Basins in Indonesia
Conduction Dominated – Orogenic Belt Type
1. Sunda Orogeny : Java Southern Mountain
Ranges – Sumatera Barisan Mountain Ranges
2. Banda Orogeny : Sulawesi Mountain Ranges
3. Melanesia Orogeny : West Papua – Papua
New Guinea Mountain Ranges
4. Talaud Orogeny : Talaud – Tifore ridge
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The potential of conductive dominated – in orogenic belts
• Sunda Orogeny
• Melanesia Orogeny
• Banda Orogeny
• Talaud Orogeny
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Concuding remark:
The Future Exploration and Utilization
Challenges and Opportunities
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• Integrating tectonic and regional geology to
better understand the geothermal system
both for volcanic – magmatic or non volcanic
• Collecting radiometric dating as many as
possible
• Start to carry out exploration program in
conduction dominated
• Think out of the box…
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……. Thank You …..
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