Geothermal Resource Conceptual Model Workshop...2016/10/21 · Geothermal Resource Conceptual...
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Geothermal Resource Conceptual Model Workshop
21-22 October 2016
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Geothermal Resource Conceptual Models For Resource Capacity and Well Targeting
William Cumming
Cumming Geoscience, Santa Rosa CA [email protected]
Office: +1-707-546-1245 Mobile: +1-707-483-7959 Skype: wcumming.com
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Geothermal Resource Conceptual Models
Geothermal Resource Conceptual Model Workshop
3
• Joe Moore asked me to arrange the workshop
• Adaptation of Geothermal Resource Decision Workshops for Companies and Institutions
• 5+ day workshops with homogeneous participants
• Single presenter and coach
• GRC Conceptual Model Workshop
• 2 days with unknown participants
• Many expert presenters and coaches
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Geothermal Resource Conceptual Models
Course Expectations
4
• Components of a geothermal conceptual model
• Basic steps to construct a geothermal conceptual model
• Types of data and types of expertise needed
• Using models in well targeting and capacity assessment
• Targeting conceptual models versus targeting data
• Decision making issues when using conceptual models
• Strengths and weaknesses of a conceptual model approach
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Geothermal Resource Conceptual Models
Schedule
5
Friday- 8-5pm
• Continental breakfast 7:30am
• AM break: 10:00-10:15
• 12:00-1:00 pm-Lunch at the Hyatt Regency
• PM break: 3:00-3:15
Saturday- 8-5pm
• A continental breakfast will be in the room as of 7:30am
• AM break: 10:00-10:15
• 12:00-1:00 pm-Lunch at the Hyatt Regency
• PM break: 3:00-3:15
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Geothermal Resource Conceptual Models
Logistics
6
• Exercises in teams of 4 or 5 with 1 coach each
• 1st and 3rd table turn around
• At coffee, distribute experience in teams
• Paper handouts to coaches
• References on USB
• Presenters put yours together and I will assemble
• Distribute USBs to presenters
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Geothermal Resource Conceptual Models
Workshop Agenda Day 1
7
Introduction to workshop (Bill Cumming)
Part 1: Volcano-hosted geothermal resource conceptual model • Conceptual models and decision making (Bill Cumming) 20 min
• Volcanic geology, structure (Glenn Melosh) 20 min
• Geochemistry (Elisabeth Easley) 20 min
• Thermodynamics of conceptual models (John Murphy) 20 min
• Exercise 1: Volcano-hosted hand-outs on geology, geochemistry and BPD.
• Resource capacity PDF from power density (Max Wilmarth) 20 min
• Vapor core systems and exploration options (Rich Gunderson) 20 min
• High temperature conceptual model construction (Steve Sewell) 20 min
• Exercise 2: Build conceptual models for P10. P50 and P90 capacity and targets.
• Well temperature log interpretation (John Murphy) 20 min
• Exercise 3: Hand out results of first 4 wells. Rebuild conceptual models.
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Geothermal Resource Conceptual Models
Workshop Agenda Day 2
8
• Indicative parameters for arc volcano reconnaissance (Peter Stelling) 20 min
• Polemic on multiple models (Glenn Melosh) 10 min
• Exercise 4: Hand out final 2 wells. Reassess capacity.
• Presentation of real field case history and NPV prize (Ken Mackenzie) 20 min
Part 2: Fault-hosted geothermal resource conceptual model
• Introduction to fault-hosted geothermal exploration (Bill Cumming) 15 min
• Structural targeting of fault-hosted geothermal systems (Nick Hinz) 30 min
• Exercise 5: Fault-hosted geology, structure, geochemistry. Recommend program.
• Exercise 6: Hand-out TGH data. Build P10. P50 and P90 models and target wells
• Structure, lithology and open space fracture permeability (Nick Hinz) 20 min
• Exercise 7: Hand out well temperatures, production and borehole lithology and structure. Revise models, capacity and targets.
• Reservoir engineering <180C fault-hosted systems with outflows (John Murphy) 20 min
• Exercise 8: Hand out final wells. Reassess capacity.
• Presentation of actual field case history (Dick Benoit) 20 min
• Conclusions and acknowledgements: (Bill Cumming) 10 min
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Geothermal Resource Conceptual Models
Geothermal Exploration Questions
Integrate geophysics with geochemistry and geology in a consistent geothermal conceptual model to answer:
1. Does a conventional geothermal reservoir exist?
2. If it exists, how big is it?
3. What is the lowest cost well targeting strategy to discover, then prove, and then develop the resource?
© Cumming (2013)
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Geothermal Resource Conceptual Models
Exploration Data to Assess Geothermal Resources Is it there? • POSexpl = Ptemperature * Pchemistry * Ppermeability
– Temperature: Water and gas geochemistry on all features – Chemistry: Same as temperature but using process plots
– Permeability: Resistivity imaging to base of impermeable clay cap. Structural model. Map of thermal features and altered ground.
• Case histories and analogies
If yes, how big is it? P10, P50, P90 area • Area: Conceptual model outlines from resistivity, geochemistry, alteration,
structure, geology etc. • Power Density: Analogous fields, plausible MW/km2 • Field analogies provide check on probabilistic approaches
Lowest cost exploration strategy • Lowest cost well target order to failure or success
• Access and hazards: Review access and hazards
• Environmental etc: Assess risk for permit denial etc.
© Cumming (2013)
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Geothermal Resource Conceptual Models
Geothermal Geoscience Conceptual Context
Basic physics of permeable geothermal reservoirs (non-EGS)
• Geothermal reservoirs lose energy to surface through any rock by heat conduction and through leaky rocks by buoyant advection of hot fluid
• In proportion to stored energy, a geothermal reservoir emits energy at a rate orders of magnitude higher than O&G reservoirs
• The geothermal emphasis on “seeps” does not indicate primitive technology relative to O&G but a difference in resource physics
Implications for geothermal exploration strategy
• Geothermal reservoirs with vertical permeability “leak” heat upward, so “hidden” systems without near-surface manifestations are “special”
• Most cost-effective reduction of risk for geothermal resource with thick vertical permeability is to demonstrate permeability and temperature using water chemistry, if not from springs then from shallow wells
© Cumming (2013)
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Geothermal Resource Conceptual Models
Geothermal Resource Setting
Moeck (2015, Geothermics) Geologic setting • Divergent (rift) • Convergent (arc) • Transform (pull-apart) • Major volcanism • Intracontinental rifts Moeck play type • Magmatic volcanic • Magmatic plutonic • Extensional • Non-convecting plays Others argue • >230°C flash • <180°C pumped • 150 to 230°C gassy
flash
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Geothermal Resource Conceptual Models
Generic Geothermal Conceptual Model Elements
13
Distributed Permeability Upflow Small Outflow
Single Fault Zone Upflow Large Shallow Outflow
Cumming (2013)
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Geothermal Resource Conceptual Models
Anomaly Hunting
• Rationale • Works by analogy
• Pitfalls • Conceptual relevance to new targets not
considered, just outcomes
• Other data not conceptually integrated
• Not directly tested by wells
• Drill a 5 ohm-m anomaly and it remains 5 ohm-m
• Remedy • Use for early and low cost decisions
• For high cost decisions, use conceptual models
to support team risk assessment
© Cumming (2013)
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Geothermal Resource Conceptual Models
Ohaaki Geothermal Field Map View “Boundary” Interpretation
from: Ussher 2007
© Cumming (2013)
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Geothermal Resource Conceptual Models
Ohaaki Geothermal Field Alteration Cross-section
after: Simmons and Browne 1998
NW SE 38 15 8 19 13 25 16 7
-1000 m --
-2000 m --
Smectite-illite clay
Illite clay
© Cumming (2013)
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Geothermal Resource Conceptual Models
Ohaaki Geothermal Field MT Resistivity Cross-section
250°C
150°C
after: Ingham 1990
S N 29 10 14 1
-1000 m --
-2000 m --
275°C
< 10 ohm-m MT 1D resistivity
27
© Cumming (2013)
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Geothermal Resource Conceptual Models
Conceptually Defined Resource Outline
from: Ussher 2007
• Closer to the productive reservoir outline
than the original “Resistivity Boundary”
© Cumming (2013)
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Geothermal Resource Conceptual Models
Resource Risk Assessment at Ohaaki
from: Ussher 2007
• Competing outlines based on conceptual model and anomaly hunting
approaches could have been reconciled as P50 and P20 outlines.
P20
P90
© Cumming (2013)
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Geothermal Resource Conceptual Models
Conceptual Models
• Rationale • Decisions based on analogous experience
• Conceptual differences considered
• Directly tested by wells
• Pitfalls • Who can integrate geophysics, geochemistry,
geology, reservoir engineering …
• Multiple models require risk assessment
• Proposed Remedy • Training on building conceptual models and
assessing risk using case histories
Cumming Geoscience
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Geothermal Resource Conceptual Models
Generic Geothermal Conceptual Model Elements
21
Distributed Permeability Upflow Small Outflow
Single Fault Zone Upflow Large Shallow Outflow
Cumming (2013)
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Geothermal Resource Conceptual Models
Geothermal Conceptual Model Elements
• Hydrology, especially deep water table but also perched aquifers • Isotherm pattern consistent with pressure and permeability • Heat Source
• Deep benign hot buoyant upflow in fractures
• Formations and alteration favorable to open space fracture permeability (and often primary permeability at shallower depths)
• Smectite Clay Cap (commonly combined cap, rarely, non-smectite cap, very rarely for commercial systems, uncapped)
• Faults creating permeable zones, flow barriers and field boundaries
• Reservoir temperature outflow with buoyant flow updip below clay cap (in liquid systems)
• Sub-commercial outflow with buoyant flow updip below clay cap (in liquid systems)
• Cold meteoric water flow down-dip into reservoir
© Cumming (2013)
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Geothermal Resource Conceptual Models
Geothermal Conceptual Model Isotherm Properties
• Isotherms define the permeable reservoir
• Isotherms are constrained by hydrothermodynamics: • Water table defines pressure and maximum temperature distribution
• Temperature < hydrostatic boiling point
• Hot upflow and outflow by buoyancy in permeable zones
• Cold influx by hydrostatic gravity flow in permeable zones with colder or higher elevation source and aquifer connection
• Conduction where permeability low
• Very high temperature gradients require permeable high and low temperature zones on each side of an impermeable zone
• No isolated hot or cold zones (cross-sections use arrow heads/tails)
Cumming (2009, Stanford; 2016, GRC)
© Cumming (2013)
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Geothermal Resource Conceptual Models
Generic Geothermal Conceptual Model Elements
24
Distributed Permeability Upflow Small Outflow
Single Fault Zone Upflow Large Shallow Outflow
Cumming (2013)
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Geothermal Resource Conceptual Models
Deep Heat Source
• Hydrothermal reservoir that will supply the produced fluid and its connection to what is known from the surface are crucial parts of the model
• Most heat sources poorly connected and uncertain so treated as boundary condition
• However, basalt magma imaged using MT or MEQ at 2 to 4 km depth can constrain 350°C and reservoir base
Melosh (2013, USAID/GEA)
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Geothermal Resource Conceptual Models
Geothermal Conceptual Model Elements
• Hydrology, especially deep water table but also perched aquifers • Isotherm pattern consistent with pressure and permeability • Heat Source
• Deep benign hot buoyant upflow in fractures
• Formations and alteration favorable to open space fracture permeability (and often primary permeability at shallower depths)
• Smectite Clay Cap (commonly combined cap, rarely, non-smectite cap, very rarely for commercial systems, uncapped)
• Faults creating permeable zones, flow barriers and field boundaries
Reflection seismic presentation
• Reservoir temperature outflow with buoyant flow updip below clay cap (in liquid systems)
• Sub-commercial outflow with buoyant flow updip below clay cap (in liquid systems)
• Cold meteoric water flow down-dip into reservoir © Cumming (2013)
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Geothermal Resource Conceptual Models
“Standard” Geoscience Plan >200°C Geothermal Exploration
• Gas and fluid geochemistry for existence and conceptual target
• MT to map base of clay “cap”
• Maybe TEM for MT statics
• Geology, alteration and structure for context
• Shallow hydrology for context
© Cumming (2013)
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Geothermal Resource Conceptual Models
Geothermal Resource Capacity Assessment for Exploration
Is it there? POSexpl = Ptemperature * Pchemistry * Ppermeability
• Based on O&G probabilities for essential resource existence – Trap, Source, Maturation range, Migration path, etc
• Reductionist
Alternative approaches • e.g. Case history analogs
© Cumming (2013)
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Geothermal Resource Conceptual Models
Geothermal Resource Capacity Risk Tree Probabilities for 5 cases at economically significant decision • Exploration success and failure • Appraisal success and failure • 3 development cases
Cumming
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Geothermal Resource Conceptual Models
• Classic studies on decision making and risk
– Kahneman (1972 etc) Cognitive biases • Cognitive pitfalls are common when uncertainty is unfamiliar
• It takes decision practice to avoid pitfalls
– Klein (2000s) Experience vs Analysis • Some decisions need experience, so how do you get experience?
• What decisions benefit from more data and analysis ?
• What types of analyses mislead ? More complex implies more risk
– Gigerenzer (1980s) Fast and frugal • e.g. Rules of thumb tested for scope and effectiveness
– Tetlock (2000s) Superforecasters • e.g. reframing for constraints, baseline probabilities
Decision Pitfalls and Solutions
Cumming Geoscience
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Geothermal Resource Conceptual Models
Conceptual Model Uncertainty • Deeper reservoir
isotherm pattern inferred from shallow geometry, long memory geothermometers and analogous reservoirs
• Uncertainty in inference of isotherm pattern increases if clay cap differs from analysts’ case history experience
© Cumming (2013)
Cumming 2007
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Geothermal Resource Conceptual Models
Geothermal Conceptual Model 2 • Base of clay cap from
< 10 ohm-m resistivity follows topography
• Top of apparent propylitic alteration 700 m above water table
© Cumming (2013)
Cumming 2007
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Geothermal Resource Conceptual Models
Geothermal Conceptual Model • Base of clay cap from
< 10 ohm-m resistivity follows topography
• Top of apparent propylitic
alteration 700 m above
water table
• Zone between water table
and base of the clay cap
commonly interpreted as
steam cap
© Cumming (2013)
Cumming 2007
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Geothermal Resource Conceptual Models
Geothermal Conceptual Model • Base of clay cap from
< 10 ohm-m resistivity follows topography
• Top of apparent propylitic alteration 700 m above water table
• Zone between water table and base of the clay cap commonly interpreted as steam
• Pressure at top of steam zone exceeds frac pressure but no leakage
© Cumming (2013)
Cumming 2007
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Geothermal Resource Conceptual Models
Geothermal Conceptual Model • Commonly observed
model consistent with lack of leakage
• Top of apparent propylitic alteration 700 m above water table but relict (cold) and low permeability
• Reservoir smaller
• Look for surface exposure of chlorite in deep drainages to confirm
© Cumming (2013)
Cumming 2007
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Global occurrence of geothermal systems in different geologic settings: their
identification and utilization
Mar-2016
William Cumming
Cumming Geoscience, Santa Rosa CA [email protected]
Office: +1-707-546-1245 Mobile: +1-707-483-7959 Skype: wcumming.com
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Geothermal Resource Conceptual Models
Geothermal Geoscience Conceptual Context
Basic physics of permeable geothermal reservoirs (non-EGS)
• Geothermal reservoirs lose energy to surface through any rock by heat conduction and through leaky rocks by buoyant advection of hot fluid
• In proportion to stored energy, a geothermal reservoir emits energy at a rate orders of magnitude higher than O&G reservoirs
• The geothermal emphasis on “seeps” does not indicate primitive technology relative to O&G but a difference in resource physics
Implications for geothermal exploration strategy
• Geothermal reservoirs with vertical permeability “leak” heat upward, so “hidden” systems without near-surface manifestations are “special”
• Most cost-effective reduction of risk for geothermal resource with thick vertical permeability is to demonstrate permeability and temperature using water chemistry, if not from springs then from shallow wells
© Cumming (2013)
![Page 38: Geothermal Resource Conceptual Model Workshop...2016/10/21 · Geothermal Resource Conceptual Models Workshop Agenda Day 2 8 • Indicative parameters for arc volcano reconnaissance](https://reader035.fdocuments.us/reader035/viewer/2022062920/5f02c4267e708231d405e7b2/html5/thumbnails/38.jpg)
Geothermal Resource Conceptual Models
Geothermal Resource Setting
Moeck (2015, Geothermics) Geologic setting • Divergent (rift) • Convergent (arc) • Transform (pull-apart) • Major volcanism • Intracontinental rifts Moeck play type • Magmatic volcanic • Magmatic plutonic • Extensional • Non-convecting plays Others argue • >230°C flash • <180°C pumped • 150 to 230°C gassy
flash
![Page 39: Geothermal Resource Conceptual Model Workshop...2016/10/21 · Geothermal Resource Conceptual Models Workshop Agenda Day 2 8 • Indicative parameters for arc volcano reconnaissance](https://reader035.fdocuments.us/reader035/viewer/2022062920/5f02c4267e708231d405e7b2/html5/thumbnails/39.jpg)
Geothermal Resource Conceptual Models
Geothermal Resource Power Density
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Geothermal Resource Conceptual Models
East EARS Development Analogy
Melosh (2013, GEA)
5 - 7 km
2 -
3 k
m
350°C
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Geothermal Resource Conceptual Models
Awibengkok Geothermal Field
Melosh (2013, GEA)
Awibengkok 377 MW
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Geothermal Resource Conceptual Models
West EARS Development Analogy
42
Geothermex (2008)
BRADYS CROSS-SECTION
2 km
1 k
m
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Geothermal Resource Conceptual Models
East versus West EARS Development Analogies
Melosh (2013, GEA)
Bradys 15 – 20 MW Awibengkok 377 MW