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 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

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

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

Geothermal Power in U.S. 0.38% of Country’s Generation California2,294 MW California2,294 MW Nevada 196 MW Nevada 196 MW Hawaii 25 MW Hawaii 25 MW Utah 31 MW Utah 31 MW TOTAL 2,400 MW TOTAL 2,400 MW

HIGH ENTHALPY FIELDS & PROSPECTS Pacific “Ring of Fire”

Exploration “Oil seep” analogy

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

Geothermal Basics Extracting the Heat Commercially n Water transports heat to surface n Naturally fractured rock permits circulation n Drill to reach at least 200° C n Future technology may use man-made fractures

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

Example: Vapor-Dominated High Enthalpy Resource

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

Example: Liquid-Dominated High Enthalpy Resource

Medan S u m a t r a Kalimantan Sulawesi Jakarta SALAK PROJECT 330 MW Unocal 330 MW in Java, Indonesia Liquid-dominated º C km deep

CROSS-SECTION THROUGH AWIBENGKOK FIELD

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

Turbine and Generator

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

Optimize exploited geothermal systems

Life Cycle of a Geothermal Field (Lovekin, 1998) Time ----> developmaintaindeclinesustain MW

Opportunity n Only a fraction (~20%) of available heat is currently extracted from a high enthalpy reservoir n Smart injection management could greatly increase efficiency and longevity n The Salak “natural laboratory” presents a unique opportunity to examine fractured- system behavior

Challenge n Reservoirs have km-scale fracturing: »hard to map permeability at km-scale »heat transfer properties poorly known »current models inadequate n Injected liquids are channeled along fractures and heat sweep is inefficient

Research: Characterize permeability and heat transfer in fractured systems

Image Log: Salak Well FMI

Salak Tracer pathways

Tracer Returns at Salak

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

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

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

Reduce development cost of high enthalpy systems

Reducing development costs n Drilling Technology n Energy Conversion Technology

Challenges n Need active continuous drilling programs to create improvements in drilling n Geothermal industry too small to attract research in service companies n Geothermal turbines are not designed and built in the U.S.

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

Drilling Cost Reduction at Salak DAYS PER WELL AWIBENGKOK EXPANSION

Geothermal The Benefits

Power Plant CO 2 Emissions Fossil fuel data from Goddard and Goddard (1990) Unocal data includes The Geysers

Capacity Factors Source: DOE/Energy Information Agency: data for 1996 WindSolarConv.AverageBiomass/FossilGeothermal HydroMSW Percentage

U.S. Government Royalties $ Millions

Conclusions n Ultimate geothermal resource is huge n Present research focus should be: –extend life of existing fields, –reduce cost of developing new high enthalpy projects n Artificially stimulated systems (HDR/EGS) hold greatest opportunity in the long term n HDR/EGS research should focus on technology which can be tested in existing fields

The End