1. SLIM HOLE GEOTHERMAL RESERVOIR CHARACTERIZATION FOR RISK REDUCTION
Dennis L. Nielson
DOSECC Exploration Services, LLC
Salt Lake City, Utah USA

2. DOSECC EXPLORATION SERVICES, LLC Mission Statement
DOSECC Exploration Services Designs, Builds and Applies Innovative Drilling Technology for Scientific, Natural Resource and Geotechnical Investigations

3. DOSECC Exploration Services
Background in Scientific Drilling with a Focus on Sample Quality
Geothermal Slim Hole Reservoir Characterization
Innovative Equipment Design & Fabrication
Lake & Shallow Marine Drilling
Soft Sediment Sampling Tools
Hard Rock Coring
Mining
Science

5. DOSECC Exploration Services, LLC EQUIPMENT DESIGN & FABRICATION
Rapid Access Ice Drill (RAID)
Design Drilling Depth: 3,300 meters
Unique Fluid Circulation System-ESTISOL 140
Wireline Tools – Drilling & Coring
Operating Elevation: 4,000 m
Operating Temperature: -55o C
Fabrication Complete-Shipped to Antarctica
Field Trials in 2016

7. INTRODUCTION SLIM HOLE GEOTHERMAL RESERVOIR CHARACTERIZATION
Geothermal Exploration is Expensive and High-Risk.
In the US, Obvious Hot Spring Areas have been Drilled, and Exploration Focus is Now on Higher Risk Buried Systems.
Price of Electricity Does Not Reflect Overall Level of Risk.
Early Stage Exploration is Often Subsidized by Governments or International Funding Organizations

8. GEOTHERMAL EXPLORATION
Risk is Mitigated by Specialized Knowledge
Geothermal Professionals
Conceptual Models
Experience: Data from Both Successes and Failures
Failures Not Often Publicized

9. SUBSURFACE RISK Impediment to Geothermal Development
Resource Risk: Size and Quality of a Reservoir
Drilling Risk: Well Completion and Fluid Production
Mechanical
Resource
Sustainability Risk: Capacity to Sustain Production through Life of a Project

10. TRADITIONAL EXPLORATION STRATEGIES
GEOLOGIC (CONCEPTUAL) MODELS and Refinement at Each Stage of Exploration
Regional (>103 Km2) to Prospect (~10’s Km2)
Less to More Expensive Methodologies
Drilling
Generates and Uses Large Amounts of Data

11. TRADITIONAL EXPLORATION STRATEGIES
GEOLOGIC (CONCEPTUAL) MODELS and Refinement at Each Stage of Exploration
Regional (>103 Km2) to Prospect (~10’s Km2)
Less to More Expensive Methodologies
Drilling
Generates and Uses Large Amounts of Data

12. Standard Practice to Drill Production Wells For Reservoir Tests
Reservoir Knowledge is Low and Risk is High
Reasons Given:
Large-Diameter Wells Required For Reservoir Engineering
Slim Hole will not Produce Fluids
Tradition
Paradigm Shift Needed to Manage Risk

13. PLAY FAIRWAY RISK MATRIX (Fugelli and Olsen, 2005)
High
Database
Confidence
Low
Low
High
Geological Model
Confidence

14. INITIAL GEOLOGIC MODEL “PLAY”
COMPONENTS
Heat Source
Reservoir Volume
Recharge
Seal
ECONOMIC VIABILITY

15. MATURE GEOLOGIC MODEL PROSPECT to DEVELOPMENT
3-D MODEL
Lithology
Physical Properties
Faults (Permeability)
System Boundaries
Fluid Chemistry
SITE and DRILL SUCCESSFUL PRODUCTION WELLS

16. SLIM HOLE DRILLING TECHNIQUES
Generally Defined as <5-inches (<12.7 cm) in Diameter.
Wireline Diamond Coring Using Mining-Style Rig
Hybrid Systems Using Large Rotary Rig plus High-Speed Top Drive
Mining-Style Rig Using Mud Motor
Rigs Not Optimized for Geothermal

17. RESERVOIR CHARACTERIZATION SLIM HOLE
Drilling
Casing
9-5/8" hole to 30 m
6-5/8" cemented
6" hole to 300 m
4-1/2" Surface
cemented
HQ Core 300 to
HQ Liner
1200 m
NQ Core 1200 to 2000 m
RESERVOIR CHARACTERIZATION SLIM HOLE
COST: ~$1,200,000 for 2000 meter hole.
Not a Production Well with Smaller Casing!
Not a Temperature Gradient Hole!

18. RESERVOIR CHARACTERIZATION SLIM HOLE
Penetrates to Reservoir Depth
Data Collection
Geology (lithology, fluid inclusions, fracture density, alteration mineralogy)
Geophysics (Temperature, Electrical Resistivity, Density, Magnetic Susceptibility)
Geochemistry (Fluid Composition)
Reservoir Engineering
Production Well Design

19. EXPERIENCE Scientific Projects
Valles Caldera, New Mexico USA
Hawaii Scientific Observation Holes, Hawaii USA
Geothermal Assessment of Ascension Island, South Atlantic
Unocal and Other Indonesian Exploration
Slim Hole Reservoir Engineering (Garg)
Oguni, Japan
Sumikawa, Japan
Takagami, Japan
Kirishima, Japan
Steamboat Hills, Nevada USA
Snake River Plain, Idaho USA
Three ~2,000 m Reservoir Assessment Holes

22. RESERVOIR ENGINEERING
Predict Discharge Characteristics of Production Wells based on Discharge From or Injection Into Slim Holes
Confirmed by Garg and Combs (1997)
Testing: If the slimhole does not flow, perform an injection test while recording fluid injection rate and temperature, and downhole (with pressure/temperature tool located close to the fluid entry) pressure and temperature.
To first order: Injectivity index ~ Productivity index

23. Temperature - Depth Mountain Home AFB, Idaho
MH-1 (1986) Tmax = 1219 m
MH-2 Flow 1745 m
Extrapolated T ~150oC
Fluid Inclusions: oC
Flowing 1355 m = 135oC

24. ARTESIAN FLOW FROM Mountain Home - 2
NQ Drill Rods
Depth to Flow Zone: 1745 m (5726 ft.)
Volume Estimates: 11 gpm
Flowing Temperature at 1355 m: 134.6o C

25. RESERVOIR CHARACTERIZATION SLIM HOLE PROGRAM
Systematic 3-D Sampling of the Reservoir
Density: 1 to 1.5 Holes/Km2
Temperature and Permeability Distribution
Reservoir Boundaries
Up-Flow, Out-Flow, Recharge
Design Production and Injection Well Drilling Program
Holes Used for Monitoring or Injection

26. DRILLING COST BASELINE
Geothermal Well Cost
Mansure & Blankenship (2011)
Crystalline Rock
High Temperature
Large Diameter
Oil & Gas Well Costs
Joint Association Survey on Drilling Costs
Sedimentary Rocks
Lower Temperature
Multiple Well Programs

27. PRODUCTION WELL “SUCCESS RATE” LEARNING CURVE EFFECT
Exploration
Development
Operation
IFC (2013)
50%
74%
83%
Hance & Gawell (2005)
25%
60%
80%
Sanyal & Morrow (2011)
55%
75%
Molloy (1982)
45% (11 wells)
15% (13 wells)

28. PRODUCTION WELL “SUCCESS RATE” LEARNING CURVE EFFECT
Exploration
Development
Operation
IFC (2013)
50%
74%
83%
Hance & Gawell (2005)
25%
60%
80%
Sanyal & Morrow (2011)
55%
75%
Molloy (1982)
45% (11 wells)
15% (13 wells)
No Conceptual Model to Guide Well Locations
Mechanical Well Failure

29. GEOTHERMAL DEVELOPMENT TASKS 50 MWe (ESMAP, 2012)
Preliminary Survey $ 2,000,000
Exploration $ 3,000,000
Test Drilling $ 18,000,000
Project Review & Planning $ 7,000,000
Field Development $ 70,000,000
Construction $ 91,000,000
Startup & Commissioning $ 5,000,000
$196,000,000

30. GEOTHERMAL DEVELOPMENT TASKS 50 MWe (ESMAP, 2012)
Preliminary Survey $ 2,000,000
Exploration $ 3,000,000
Test Drilling $ 18,000,000
Project Review & Planning $ 7,000,000
Field Development $ 70,000,000
Construction $ 91,000,000
Startup & Commissioning $ 5,000,000
$196,000,000

31. INVESTMENT for 50MWe DEVELOPMENT
ESMAP, 2012

32. RISK vs. INVESTMENT for 50MWe DEVELOPMENT
ESMAP, 2012

33. GEOTHERMAL SLIM HOLES VS. PRODUCTION WELL COSTS

34. PRO FORMA 50 MWe PROJECT TEMPERATURE: 250o C VOLUME: 32 km3
SURFACE AREA: 16 km2
RESERVOIR DEPTH: 1000 to 3000 m
DRILLING DEPTHS: 2000 m
SLIM HOLE COST: $1,200,000
PRODUCTION WELL COST: $4,500,000
RESERVOIR TESTING: $250,000/WELL
ASSUME 5 MWe per Production Well

35. PRO FORMA 50 MWe PROJECT SLIM HOLES PRODUCTION WELLS One hole/km2 = 16
Drilling : $19,200,000
Testing: $ 4,000,000
$23,200,000
OBJECTIVE: Increase PSUCCESS to 80% Due To Learning Curve
Enable Decision on System Development
77% SUCCESS RATE (10/13)
Drilling: $ 58,500,000
Testing: $ 3,250,000
$61,750,000

36. GEOTHERMAL DEVELOPMENT COSTS 50 MWe
                                 

37. CONCLUSIONS
Slim Hole Reservoir Characterization Program Provides Better Coverage at Lower Cost Compared to Production Well Drilling.
Exploration is Knowledge Based as Demonstrated in the Play Fairway Approach.