GEOTHERMAL RESERVOIR ENGINEERING IN THE UNITED STATES SINCE THE 1980S

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GEOTHERMAL RESERVOIR ENGINEERING IN THE UNITED
STATES SINCE THE 1980S

• John W. Pritchett
• Thirty-First GRC
• Annual Meeting
• Sparks, Nevada
• October 2, 2007

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ACTIVITY DIAGNOSTIC 1RESERVOIR ENGINEERING
PAPERS PRESENTED AT THE ANNUAL GRC MEETING
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ACTIVITY DIAGNOSTIC 2ANNUAL STANFORD
GEOTHERMAL RESERVOIR ENGINEERING WORKSHOP PAPERS
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• SO, BASED ON PUBLICATION VOLUME, GEOTHERMAL
  RESERVOIR ENGINEERING APPEARS TO BE REASONABLY
  HEALTHY.
• WHICH IS SURPRISING, IN VIEW OF HOW THE
  ENVIRONMENT FOR GEOTHERMAL RESERVOIR ENGINEERING
  HAS CHANGED IN THE U.S. SINCE THE EARLY 1980S.
• FOR INSTANCE

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RESOURCE COMPANIES ACTIVE IN U. S. GEOTHERMAL IN
THE 1980S

• HUNT
• KENNECOTT
• OCCIDENTAL
• SHELL
• SIGNAL
• UNOCAL

• AMINOIL
• ANADARKO
• ARCO
• BURMA
• CHEVRON
• GETTY

MOST OUT OF GEOTHERMAL BY 1989
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WHAT WENT WITH THEM?

• FINANCIAL RESOURCES STABILITY
• RESERVOIR ENGINEERING EXPERTISE
• INVESTMENTS IN NEW TECHNOLOGY
• FAMILIARITY WITH RESOURCE RISK
• APPRECIATION OF THE IMPORTANCE OF RESERVOIR
  MANAGEMENT

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THEN, IN THE 1990S

• IN 1992, LARGE-SCALE GEOTHERMAL PROJECT
  DEVELOPMENT CEASED IN THE U.S. BECAUSE OF
  COMPETITION FROM CHEAP NATURAL GAS AND THE DEMISE
  OF STANDARD OFFER FOUR.
• U.S. PROJECT DEVELOPERS MOVED OVERSEAS, MAINLY TO
  ASIA, DURING THE 1990S.
• THE 1997-1999 ASIAN FINANCIAL CRISIS ABRUPTLY
  TERMINATED THIS EXPANSION, WITH ABANDONED
  PROJECTS AND HEAVY FINANCIAL LOSSES.
• PUBLIC FUNDING BECAME THE LAST HOPE FOR U.S.
  RESERVOIR TECHNOLOGY DEVELOPMENT.

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FEDERAL GEOTHERMAL RD SUPPORT, FY 1974 FY 2006
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PITFALLS OF DECLINE-CURVE
FORECASTING
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AND EVEN MORE BAD NEWS

• THE JAPANESE GOVERNMENTS GEOTHERMAL RD PROGRAM,
  THE WORLDS LARGEST AT 100M (U.S.) / YEAR SINCE
  THE EARLY 1980S, WAS ABRUPTLY TERMINATED IN
  APRIL 2003.
• INTERNATIONAL GEOTHERMAL TRAINING PROGRAMS CEASED
  OPERATIONS IN ITALY (1993), JAPAN (2001), AND NEW
  ZEALAND (2003), LEAVING ONLY THE U.N. UNIVERSITY
  PROGRAM IN ICELAND STILL OPERATING.

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WITH ALL THIS BAD NEWS, HOW CAN WE EXPLAIN THE
APPARENT SUSTAINED ACTIVITY IN GEOTHERMAL
RESERVOIR ENGINEERING?
SO,

• SAFE HARBORS?
• MATURITY OF THE COMMUNITY?
• GROWTH OF THE INDUSTRY?
• GLOBALIZATION?
• RESOURCE DIVERSITY?
• TECHNOLOGICAL INNOVATIONS?

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1. SAFE HARBORS

• NUCLEAR WASTE ISOLATION
• CO2 SEQUESTRATION
• OIL AND GAS

DUAL PUBLICATION IN THE GEOTHERMAL LITERATURE MAY
MASK A DECLINE IN GEOTHERMAL RESERVOIR
ENGINEERING.
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2. MATURITY OF THE COMMUNITY

• 1975-1982 CLASS OF RESERVOIR ENGINEERS IS NOW
  APPROACHING RETIREMENT AGE.
• FEW HAVE ENTERED THE FIELD SINCE.
• OLDER PROFESSIONALS USUALLY PRODUCE MORE
  PUBLICATIONS, BUT
• WHO WILL GIVE THE NEXT TWENTY-YEAR RESERVOIR
  ENGINEERING RETROSPECTIVE AT THE GRCS 51st
  ANNUAL MEETING IN 2027?

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3. GROWTH OF THE INDUSTRY
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4. GLOBALIZATION

• THE PERCENTAGE OF RESERVOIR ENGINEERING PAPERS
  PRESENTED AT MAJOR TECHNICAL MEETINGS BY U.S.
  AUTHORS IS DECLINING.
• AT WGC2005 IN TURKEY, ONLY 6 OF ALL THE
  RESERVOIR PAPERS WERE U.S.-AUTHORED. THE U.S.
  DELEGATION RANKED 9th IN SIZE, BEHIND TURKEY,
  RUSSIA, INDONESIA, THE PHILIPPINES, ICELAND, NEW
  ZEALAND, JAPAN AND CHINA.
• LESS THAN 1/3 OF THE RESERVOIR ENGINEERING
  PAPERS AT THIS 2007 GRC ANNUAL MEETING HERE IN
  NEVADA ARE FROM THE UNITED STATES.

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5. RESOURCE DIVERSITY
GEOTHERMAL FIELDS IN THE UNITED STATES WITH gt 10
YEARS OF HISTORICAL OPERATION IN 1990 1
IN 1995 4 IN 2000 15 IN 2005 18
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6. TECHNOLOGICAL INNOVATIONS

• RESERVOIR ENGINEERS ARE NOW MORE
• EFFICIENT DUE TO IMPROVEMENTS IN
• A. DATA ACQUISITION / INTERPRETATION
• B. COMPUTER SPEED AND COST
• C. RESERVOIR MODELING TOOLS

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TECHNOLOGICAL INNOVATIONSA. FIELD DATA
ACQUISITION, INTERPRETATION, VISUALIZATION

• IMPROVED PRESSURE-TRANSIENT TESTING
• IMPROVED TRACER-INJECTION TESTING
• IMPROVED GEOTHERMAL LOGGING TOOLS
• IMPROVED PRODUCTION MONITORING
• TIME-LAPSE GEOPHYSICAL SURVEYS

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TECHNOLOGICAL INNOVATIONSB. ADVANCES IN
ELECTRONIC COMPUTING MACHINES

• 1980-ERA COMPUTERS WERE EXPENSIVE, SLOW
• COMPUTER-TIME COSTS DOMINATED BUDGETS
• FASTER ELECTRONICS, MASS PRODUCTION
• COMPUTER TIME NOW TOO CHEAP TO METER

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THE ONGOING COMPUTER REVOLUTION
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RESERVOIR MODEL DEVELOPMENT CIRCA 1982

• MAINFRAME ( PRICE / PERFORMANCE ) WAS 400,000
  TIMES HIGHER THAN A MODERN PC.
• CPU-TIME BILLS WERE 300 TO 800 PER HOUR FOR
  MACHINES WITH 1 THE SPEED NOW AVAILABLE USING AN
  ORDINARY 1500 DESKTOP MACHINE.
• COMPUTER BUDGET OFTEN gt LABOR COST.
• RESULT RELATIVELY CRUDE MODELS

two-dimensional porous-medium lt 1000 grid blocks
usually H2O only often single-phase lt 1000-year
natural-state
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TECHNOLOGICAL INNOVATIONSC. IMPROVED
RESERVOIR MODELING TECHNIQUES

• 1. TWO-PHASE FLOW PHENOMENOLOGY
• 2. NON-EQUILIBRIUM MODELS
• 3. NATURAL-STATE MODELING
• 4. CONSTITUTIVE REPRESENTATIONS
• 5. COUPLED RESERVOIR CHEMISTRY
• 6. GEOPHYSICAL SURVEY DATA SETS
• 7. AUTOMATED INVERSION TECHNIQUES

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MODELING TECHNIQUES1. TWO-PHASE FLOW PHENOMENA

• RELATIVE PERMEABILITY AND CAPILLARY PRESSURE
• TWO-PHASE FLOW IN FRACTURES
• MASS TRANSFER BETWEEN PHASES (evaporation and
  condensation)

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MODELING TECHNIQUES2. NON-EQUILIBRIUM MODELS

• RELAX ASSUMPTION OF LOCAL THERMODYNAMIC
  EQUILIBRIUM
• DOUBLE POROSITY MODELS (Warren-Root)
• EXPLICIT FRACTURE TREATMENT (for sparsely
  fractured systems)
• STATISTICAL (MINC-TYPE) MODELS (for densely
  fractured systems)

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MODELING TECHNIQUES3. THE NATURAL STATE

• HISTORY-MATCH STARTING CONDITIONS SHOULD BE
  NEARLY STEADY (not just pressure equilibrium).
• NATURAL-STATE CALCULATIONS USUALLY REPRESENT
  10,000 1,000,000 YEARS.
• COMPUTED NATURAL-STATE MUST MATCH DATA FROM EARLY
  EXPLORATION WELLS (further constraints on
  models).

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MODELING TECHNIQUES4. FLUID CONSTITUTIVE
MODELS

• RESERVOIR FLUIDS WITH DISSOLVED SOLIDS (i.e.
  NaCl) AND NONCONDENSABLE GASES (i.e. CO2 ) ARE
  NOW AVAILABLE.
• MULTIPLE TRACERS MAY BE INCLUDED.
• EXTREMELY HOT (supercritical) DESCRIPTIONS ARE
  ALSO AVAILABLE.

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MODELING TECHNIQUES5. CHEMICAL REACTIONS

• A FEW CALCULATIONS HAVE BEEN REPORTED
  INCORPORATING REACTIVE CHEMISTRY (many species).
• COUPLED TO FLUID FLOW BY DISSOLUTION AND
  PRECIPITATION OF SOLIDS (creation and destruction
  of porosity and permeability).
• EXTREMELY COMPUTATIONALLY INTENSIVE.

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MODELING TECHNIQUES6. TIME-LAPSE SURVEY DATA

• COMPUTATIONAL POSTPROCESSORS TO FORWARD-CALCULATE
  CHANGES IN GEOPHYSICAL SURFACE SURVEYS (gravity,
  electrical, etc.) BASED ON HISTORY-MATCH
  SIMULATIONS.
• COMPARE TO RESULTS FROM TIME-LAPSE FIELD SURVEYS.
• PROVIDES ADDITIONAL CONSTRAINTS ON HISTORY-MATCH
  FOR MODEL VALIDATION.

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MODELING TECHNIQUES7. AUTOMATED INVERSION

• AUTOMATIC RESERVOIR MODELING USING AN ITERATIVE
  INVERSION PROCEDURE TO DRIVE CONVENTIONAL FORWARD
  RESERVOIR MODELS, TREATED AS SUBROUTINES.
• USER MUST SPECIFY THE DEGREES OF FREEDOM TO BE
  VARIED AND THE OBJECTIVE FUNCTION TO BE
  MINIMIZED.
• IF DEGREES OF FREEDOM ARE NUMEROUS, EXTREMELY
  COMPUTATIONALLY INTENSIVE.

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SO THERE IS LIKELY TO BEA CONTINUING NEED
FORHUMANGEOTHERMAL RESERVOIRENGINEERS FOR AT
LEASTSEVERAL MORE DECADESTO COME.