geothermal resource conceptual model workshop...2016/10/21 · geothermal resource conceptual...

Geothermal Resource Conceptual Model Workshop

21-22 October 2016

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

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


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


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


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


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.


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


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)


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)


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)


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


Generic Geothermal Conceptual Model Elements

13

Distributed Permeability Upflow Small Outflow

Single Fault Zone Upflow Large Shallow Outflow

Cumming (2013)


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)


Ohaaki Geothermal Field Map View “Boundary” Interpretation

from: Ussher 2007

© Cumming (2013)


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)


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)


Conceptually Defined Resource Outline

from: Ussher 2007

• Closer to the productive reservoir outline

than the original “Resistivity Boundary”

© Cumming (2013)


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)


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



21



Cumming (2013)


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)


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)



24



Cumming (2013)


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)


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)


“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)


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)


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


• 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


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


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


Geothermal Conceptual Model • Base of clay cap from


• 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


Geothermal Conceptual Model • Base of clay cap from


• 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


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

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


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)


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


Geothermal Resource Power Density


East EARS Development Analogy

Melosh (2013, GEA)

5 - 7 km

2 -

3 k

m

350°C


Awibengkok Geothermal Field

Melosh (2013, GEA)

Awibengkok 377 MW


West EARS Development Analogy

42

Geothermex (2008)

BRADYS CROSS-SECTION

2 km

1 k

m


East versus West EARS Development Analogies

Melosh (2013, GEA)

Bradys 15 – 20 MW Awibengkok 377 MW

geothermal resource conceptual model workshop...2016/10/21 · geothermal resource conceptual...

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