Title: GEOTHERMAL POWER
1GEOTHERMAL POWER Ken Williamson General
Manager, Geothermal Technology
Services, Unocal Corporation WORKSHOP ON
SUSTAINABLE ENERGY SYSTEMS November 29 - December
1, 2000 Georgia Tech, Atlanta, GA
2Heat in the Earth (Rybach et al., 2000)
- Stored in the earth 1031 J
- Beneath continents (lt1km) 4.1026J
- Current Annual Usage 4.1020J
3Geothermal Power Worldwide
- 8 GWe in 21 nations
- 50 TWh generated in 1999
- In the last 5 years
- Worldwide increased by 17
- U.S. decreased 20
4Geothermal Power in U.S.0.38 of Countrys
Generation
- California 2,294 MW
- Nevada 196 MW
- Hawaii 25 MW
- Utah 31 MW
- TOTAL 2,400 MW
5HIGH ENTHALPY FIELDS PROSPECTS
Pacific Ring of Fire
6Exploration Oil seep analogy
7Geothermal Fields Developed by Unocal
8Geothermal BasicsExtracting the Heat Commercially
- Water transports heat to surface
- Naturally fractured rock permits circulation
- Drill to reach at least 200 C
- Future technology may use man-made fractures
9GEOTHERMAL RESOURCE TYPES
- Liquid-dominated
- Vapor-dominated
- Low Enthalpy
- Hot Dry Rock
10Example Vapor-Dominated High Enthalpy Resource
11 Unocal at The Geysers 1967 -1999
380 wells drilled2.5 trillion lbs steam
produced124 billion kWh generated186 million
bbl oil equiv.
12Example Liquid-Dominated High Enthalpy Resource
13Unocal 330 MW in Java, Indonesia Liquid-dominated
225 - 310Âş C 1 - 3 km deep
14CROSS-SECTION THROUGH AWIBENGKOK FIELD
15(No Transcript)
16During Project Life Produce gt10 12 lbs
steam Inject 16 billion bbl brine
17Turbine and Generator
18Proposed Research Timeline2000 - 2030
- Optimize exploited geothermal systems
reduce development cost of high enthalpy
systems - Locally enhance permeability in the tight margins
of existing systems (EGS) - Explore for and develop hidden high enthalpy
systems, with no surface features - Develop impermeable systems with artificial
fracturing (HDR) - -----gt Time
19Optimize exploited geothermal systems
20Life Cycle of a Geothermal Field (Lovekin, 1998)
develop
maintain
decline
sustain
MW
Time ----gt
21Opportunity
- Only a fraction (20) of available heat is
currently extracted from a high enthalpy
reservoir - Smart injection management could greatly increase
efficiency and longevity - The Salak natural laboratory presents a unique
opportunity to examine fractured-system behavior
22Challenge
- Reservoirs have km-scale fracturing
- hard to map permeability at km-scale
- heat transfer properties poorly known
- current models inadequate
- Injected liquids are channeled along fractures
and heat sweep is inefficient
23Research Characterize permeability and heat
transfer in fractured systems
24Image Log Salak Well FMI
25(No Transcript)
26 Salak Tracer pathways
27Tracer Returns at Salak
28Proposed Research Designer tracer cocktails
- average path temperature
- maximum path temperature
- surface contact area along flow path
29SALAK NUMERICAL MODEL FEATURES
NORTHERN OUTFLOW
SHALLOW EASTERN RESERVOIR
WESTERN OUTFLOW
DEEP WESTERN RESERVOIR
SOUTHERN OUTFLOW
30Technical ChallengeCombine sparse, complex
data to predict heat sweep in naturally fractured
systems
31Reduce development cost of high enthalpy systems
32Reducing development costs
- Drilling Technology
- Energy Conversion Technology
33Challenges
- Need active continuous drilling programs to
create improvements in drilling - Geothermal industry too small to attract research
in service companies - Geothermal turbines are not designed and built in
the U.S.
34Opportunities
- Sandia and developers collaborate in drilling
technology - Remarkable drilling improvements have occurred -
more are possible
35Drilling Cost Reduction at Salak
DAYS PER WELLAWIBENGKOK EXPANSION
36Geothermal
37Power Plant CO2 Emissions
Fossil fuel data from Goddard and Goddard
(1990) Unocal data includes The Geysers
38Capacity Factors
Percentage
Wind Solar Conv. Average Biomass/ Fossil Geotherm
al Hydro MSW
Source DOE/Energy Information Agency data for
1996
39U.S. Government Royalties
Millions
40Conclusions
- Ultimate geothermal resource is huge
- Present research focus should be
- extend life of existing fields,
- reduce cost of developing new high enthalpy
projects - Artificially stimulated systems (HDR/EGS) hold
greatest opportunity in the long term - HDR/EGS research should focus on technology which
can be tested in existing fields
41The End