GEOTHERMAL POWER. Ken Williamson. General Manager, Geothermal Technology & Services, Unocal Corporation

Transcription

1 GEOTHERMAL POWER Ken Williamson General Manager, Geothermal Technology & Services, Unocal Corporation WORKSHOP ON SUSTAINABLE ENERGY SYSTEMS November 29 - December 1, 2000 Georgia Tech, Atlanta, GA

2 Heat in the Earth (Rybach et al., 2000)! Stored in the earth J! Beneath continents (<1km) J! Current Annual Usage J

3 Geothermal Power Worldwide! 8 GW e in 21 nations! 50 TWh generated in 1999! In the last 5 years: Worldwide increased by 17% U.S. decreased 20%

4 Geothermal Power in U.S. 0.38% of Country s Generation! California 2,294 MW! Nevada 196 MW! Hawaii 25 MW! Utah 31 MW! TOTAL 2,400 MW

5 HIG H ENTHALPY FIELDS & PRO SPEC TS Pacific Pacific Ring Ring of of Fire Fire

6 Exploration Oil seep analogy

7 Geothermal Fields Developed by Unocal Philippines 756 MW Geysers 1100 MW Salton Sea 80 MW Indonesia 330 MW

8 Geothermal Basics Extracting 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

9 GEOTHERMAL RESOURCE TYPES! Liquid- dominated! Vapor- dominated! Low Enthalpy! Hot Dry Rock

10 Example: Vapor-Dominated High Enthalpy Resource

11 Unocal at The Geysers wells drilled 2.5 trillion lbs steam produced 124 billion kwh generated 186 million bbl oil equiv.

12 Example: Liquid-Dominated High Enthalpy Resource

13 MedanS u m a t r a Unocal 330 MW in Java, Indonesia Liquid-dominated º C 1-3 km deep Kalimantan Sulawesi Jakarta SALAK PROJECT 330 MW JAVA SALAK PROJECT INDEX MAP SCALE 1: KM

14 CROSS-SECTION THROUGH AWIBENGKOK FIELD

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16 During Project Life: Produce >10 12 lbs steam Inject 16 billion bbl brine

17 Turbine and Generator

18 Proposed Research Timeline » 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) -----> Time

19 Optimize exploited geothermal systems

20 Life Cycle of a Geothermal Field (Lovekin, 1998) develop maintain decline sustain MW Time ---->

21 Opportunity! 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

22 Challenge! 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

23 Re se a rc h : Characterize permeability and heat transfer in fractured systems

24 Image Log: Salak Well FMI

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26 Salak Tracer pathways 12 U1,2,3 U4,5,6 0 1 Km

27 Tracer Returns at Salak AWI 4-1 TRACER RETURNS AT AWI 1 WELLS Concentration, ppb Elapsed Tim e since Dye Injection on 1/8/99, day

28 Proposed Research: Designer tracer cocktails! average path temperature! maximum path temperature! surface contact area along flow path

29 SALAK NUMERICAL MODEL FEATURES WESTERN OUTFLOW SHALLOW EASTERN RESERVOIR NORTHERN OUTFLOW DEEP WESTERN RESERVOIR SOUTHERN OUTFLOW

30 Technical Challenge: Combine sparse, complex data to predict heat sweep in naturally fractured systems

31 Reduce development cost of high enthalpy systems

32 Reducing development costs! Drilling Technology! Energy Conversion Technology

33 Challenges! 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.

34 Opportunities! Sandia and developers collaborate in drilling technology! Remarkable drilling improvements have occurred - more are possible

35 Drilling Cost Reduction at Salak DAYS PER WELL AWIBENGKOK EXPANSION Units 1 &

36 Geothermal The Benefits

37 Power Plant CO 2 Emissions CO 2 (kg/mwh) Coal Oil Natural Gas Unocal Geothermal Fossil fuel data from Goddard and Goddard (1990) Unocal data includes The Geysers

38 Capacity Factors 100 Percentage Wind Solar Conv. Average Biomass/ Fossil Geothermal Hydro MSW Source: DOE/Energy Information Agency: data for 1996

39 U.S. Government Royalties $ Millions Wind Solar Biomass Geothermal

40 Conclusions! 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

41 The End