A New Look at Geothermal Energy as an Energy Choice for the Future

A New Look at Geothermal Energy as an A New Look at Geothermal Energy as an Energy Choice for the FutureEnergy Choice for the Future

W.D. Gosnold, D.F. Merriam, D.D. Blackwell W.D. Gosnold, D.F. Merriam, D.D. Blackwell U. North Dakota Kansas Geol. Survey Southern Methodist U.

OutlineOutlineTake home messageTake home message

Geothermal energy overviewGeothermal energy overview

What we thought we knewWhat we thought we knew

What has changed What has changed

What we now knowWhat we now know

Take Home MessageTake Home Message

Geothermal energy is an underestimated and Geothermal energy is an underestimated and largely untapped resource that could have a largely untapped resource that could have a significant impact on the world’s energy future.significant impact on the world’s energy future.Advances in technology make electrical power Advances in technology make electrical power generation from low-to-intermediate temperature generation from low-to-intermediate temperature geothermal waters a reality.geothermal waters a reality.The power that could be generated from oil field The power that could be generated from oil field waste waters alone is enormous.waste waters alone is enormous.Combining all potential geothermal resources could Combining all potential geothermal resources could supply all electrical power needs for the US.supply all electrical power needs for the US.

Image Source: Geothermal Education Office, Tiburon CA

The first coordinated assessment of US The first coordinated assessment of US geothermal resources involved:geothermal resources involved:

US Geological SurveyUS Geological Survey– Circular 726 (1975) Circular 726 (1975) – Circular 790 (1979) Circular 790 (1979) – Circular 892 (1983) Circular 892 (1983)

DOE - State Coupled ProgramDOE - State Coupled Program– Geothermal resource maps and reportsGeothermal resource maps and reports

IndustryIndustry– Working power plantsWorking power plants

UniversitiesUniversities– SMU, Utah, OIT, MIT, Va Tech, Nebraska, UND, UK, NMSU SMU, Utah, OIT, MIT, Va Tech, Nebraska, UND, UK, NMSU

– Establishment of laboratories and many publicationsEstablishment of laboratories and many publicationsProfessional OrganizationsProfessional Organizations– Geothermal Resources CouncilGeothermal Resources Council

Some key definitionsSome key definitions

The temperature scheme established by The temperature scheme established by the U.S. Geological Survey Circular 726 the U.S. Geological Survey Circular 726 (White and Williams, 1975) categorized (White and Williams, 1975) categorized hot water resources as:hot water resources as:– high-temperature (>150°C)high-temperature (>150°C)– intermediate-temperature (150°C to 90°C)intermediate-temperature (150°C to 90°C)– low-temperature (<90°C) low-temperature (<90°C)

Hydrothermal systemsHydrothermal systems

Conduction dominated systemsConduction dominated systems

Stratabound systemsStratabound systems

Geopressured systemsGeopressured systems

Engineering enhanced geothermal Engineering enhanced geothermal systems (EGS)systems (EGS)

Ground source heat pumpGround source heat pump

Types of Geothermal SystemsTypes of Geothermal Systems

Geothermal Applications

Direct use heat

Electrical power

Ground source heat pumps

1018 = exa so 1 x 1018 J = 1 EJ

1 J = 1 W s 1 EJ = 0.278 TWh

Kilo, Mega, Giga, Tera, Peta, Exa, Zetta, Yotta

Direct UseDirect Use

Space heatingSpace heatingAquacultureAquacultureGreenhousesGreenhouses Industrial processesIndustrial processes

Although the potential for energy production from Although the potential for energy production from low to intermediate resources is great, actual usage low to intermediate resources is great, actual usage has been slow to develop. has been slow to develop. Lund and Boyd (2000) estimated that direct heat Lund and Boyd (2000) estimated that direct heat applications in the United States are 8.478 EJ yapplications in the United States are 8.478 EJ y-1-1 (8,044 billion btu y(8,044 billion btu y-1-1). ). The accessible resource in sedimentary basins is The accessible resource in sedimentary basins is more than 3 x 10more than 3 x 1066 greater than the amount in use. greater than the amount in use.

Source: Geothermal Education Office, Tiburon CA


Electrical PowerElectrical Power

CountryCountry 1990 1990 MWeMWe

1995 1995 MWeMWe

2000 2000 MWeMWe

2005 2005 MWeMWe

TotalTotal 5831.725831.72 6833.386833.38 7974.067974.06 89128912

USAUSA 2774.62774.6 2816.72816.7 22282228 25442544

PhilippinesPhilippines 891891 12271227 19091909 19311931

MexicoMexico 700700 753753 755755 953953

IndonesiaIndonesia 144.75144.75 309.75309.75 589.5589.5 797797

ItalyItaly 545545 631.7631.7 785785 790790

JapanJapan 214.6214.6 413.71413.71 546.9546.9 535535


Geothermal Power Plant

Dixie Valley, Nevada

Geothermal Power Plant

The Geysers


Ground Source Heat PumpsGround Source Heat Pumps

The potential for geothermal heat pumps (GHP) The potential for geothermal heat pumps (GHP) applications is enormous and GHPs are one of the applications is enormous and GHPs are one of the fastest growing renewable energy applications world fastest growing renewable energy applications world wide (Lund et al., 2004). wide (Lund et al., 2004). The global installed capacity is estimated to be 12 GWt The global installed capacity is estimated to be 12 GWt and the annual energy use is about 72 PJ (Lund et al., and the annual energy use is about 72 PJ (Lund et al., 2004). 2004). Lund et al., (2004) determined that coupling GHP systems with renewable electricity resources results in an apparent efficiency of 140% with an excess of 40% over the original energy consumed in generating the electricity.

What we knewWhat we knew

High-temperature convection systems in the western U.S. contain 371 EJ (Renner, White, and Williams, USGS Cir. 726, 1975). Intermediate temperature systems, which exist primarily in the western U.S., contain 42 ±13 EJ (Brook et al., USGS Cir. 790, 1978).The accessible low-temperature resource base in the central United States contains 27,000 EJ (Sorey et al., USGS Cir. 893, 1983). Undiscovered low temperature resources contain an additional 7,200 EJ (Sorey et al., USGS Cir. 893, 1983).

What has changedWhat has changed

More and better data on heat flow and More and better data on heat flow and subsurface temperaturessubsurface temperatures

Technology advancesTechnology advances

Global energy economicsGlobal energy economics

Global Heat FlowGlobal Heat FlowGlobal average heat flow: 87 mW mGlobal average heat flow: 87 mW m-2-2

Total surface heat flux: 44.2 x TWTotal surface heat flux: 44.2 x TW

83% of present surface heat flow is due to 83% of present surface heat flow is due to radioactive decay of U, Th, and K radioactive decay of U, Th, and K

Earth’s mantle is cooling at a rate of 36 °C GaEarth’s mantle is cooling at a rate of 36 °C Ga-1-1

Average solar flux at the surface: 400 W mAverage solar flux at the surface: 400 W m-2-2

Average solar flux at TOA: 1365 W mAverage solar flux at TOA: 1365 W m-2-2

1984

Geothermal Map of North America,

SMU Geothermal Laboratory, 2004

D. Blackwell and M. Richards, Eds.,

USGS Circular 892: The GRA considered only USGS Circular 892: The GRA considered only one or two potential geothermal aquifers within one or two potential geothermal aquifers within well-known sedimentary basins. well-known sedimentary basins. Large basins such as the Williston Basin, Large basins such as the Williston Basin, Denver Basin, Powder River Basin, Anadarko Denver Basin, Powder River Basin, Anadarko Basin, and the US Gulf Coast region contain Basin, and the US Gulf Coast region contain more than a dozen potential geothermal aquifers more than a dozen potential geothermal aquifers having temperatures greater than 100 °C. having temperatures greater than 100 °C. LTITSLTITS Resource: Resource: LLow-ow-tto-o-iintermediate ntermediate ttemperature emperature sstratabound resourcetratabound resource

Low-to-intermediate temperatureLow-to-intermediate temperature resources were underestimated resources were underestimated

LTITS in ND and SDLTITS in ND and SD

The estimate in USGS Circular 892, based on only the principal water producing formations, the Dakota Group and the Madison aquifer, in the Williston and Kennedy basins totaled 2,050 EJ. Analysis of all potential aquifers in South Dakota and North Dakota indicates that the total accessible resource base in the two basins is approximately 33,700 EJ.If the difference between earlier assessments and the current analysis applies to similar basins, the accessible resource base for the US may be of the order of 400,000 EJ. The US LTITS resource was underestimated by 400%.

Conductive heat flow at Conductive heat flow at the surface is described the surface is described by Fourier’s Law of Heat by Fourier’s Law of Heat conductionconduction

Assuming we know heat Assuming we know heat flow, temperature at depth flow, temperature at depth “z” may be calculated by“z” may be calculated by

q

n

i

iz

qzT

1

n

i i

iz

qzT

1

Calculating the geothermal resource base

Depth Thermal Temp. Top of Unit

System Thickness70% of Max. Thickness Conductivity Gradient Temp.

(meters) (meters) (W m-1 K-1) (mK m-1) (°C)

Quaternary 510 0 1.4 42.9 6.0

Tertiary 1250 357 1.2 49.9 27.9

Cretaceous 1640 1232 1.2 48.2 71.6

Jurassic 395 2380 1.3 44.6 126.8

Triassic 225 2657 1.3 46.2 139.2

Permian 232 2814 2.9 20.7 146.4

Pennsylvanian 175 2976 1.7 35.1 149.8

Mississippian 675 3099 2.9 20.6 154.1

Devonian 770 3571 2.7 22.2 163.8

Silurian 370 4110 3.5 17.1 175.8

Ordovician 400 4369 2.7 22.6 180.3

Cambrian 300 4649 1.7 35.3 186.6

Generalized Thermostratigraphy of the Williston Basin

Three T-z profiles measured in wells in thermal equilibrium with the surrounding rocks and a model T-z profile.

Use the equilibrium temperature not the BHT

Colors are temperature, contours are depth (m), lines are county boundaries

The energy resource in Joules is the product of density*volumetric heat capacity*volume*dT qr = ρcvad (t-tref)

The Madison Fm in western North Dakota contains 1,476 EJ.

Source: "The Future of Geothermal Energy," MIT Report, January 22, 2007.

Sediment thickness in the continental United States

North DakotaNorth Dakota and Eastern Montanaand Eastern Montana

Heat flow in North Dakota and eastern Heat flow in North Dakota and eastern Montana averages 52 ± 15 mWm-2 (n=40) Montana averages 52 ± 15 mWm-2 (n=40) and ranges from 45 mW m-2 in eastern and ranges from 45 mW m-2 in eastern North Dakota to 75 mW m-2 in the North Dakota to 75 mW m-2 in the Williston basin in eastern Montana. Williston basin in eastern Montana.

The mean accessible The mean accessible LTITSLTITS resource resource base is approximately base is approximately 31,800 EJ31,800 EJ. .

Eastern ColoradoEastern Colorado

Heat flow east of the Front Range in Heat flow east of the Front Range in Colorado averages 91 ± 19 mWmColorado averages 91 ± 19 mWm-2 -2 (n=15).(n=15).

The mean accessible The mean accessible LTITSLTITS geothermal geothermal resource base is resource base is 2,640 EJ2,640 EJ..

South DakotaSouth Dakota

Anomalous heat flow due to heat advection in Anomalous heat flow due to heat advection in topographically driven ground water flow in topographically driven ground water flow in regional Paleozoic and Mesozoic aquifers regional Paleozoic and Mesozoic aquifers occurs in an 80,000 kmoccurs in an 80,000 km2 area in South Dakota area in South Dakota between the Black Hills and the Missouri River. between the Black Hills and the Missouri River. Heat flow as low as 20 mW mHeat flow as low as 20 mW m-2 occurs in the occurs in the recharge region near the Black Hills, and heat recharge region near the Black Hills, and heat flow as high as 140 mW mflow as high as 140 mW m-2-2 occurs above the occurs above the discharge region in south central South Dakota.discharge region in south central South Dakota.The mean accessible The mean accessible LTITSLTITS resource base is resource base is 12,250 EJ12,250 EJ. .

NebraskaNebraska

Heat flow in Nebraska averages about 65 Heat flow in Nebraska averages about 65 ± 20 mWm± 20 mWm-2-2 (n = 42), but the north central (n = 42), but the north central and western parts have anomalously high and western parts have anomalously high heat flow (80 to 145 mWmheat flow (80 to 145 mWm-2-2 ) due to ) due to regional groundwater flow in confined regional groundwater flow in confined aquifers.aquifers.The mean accessible The mean accessible LTITSLTITS resource resource base is base is 3,720 EJ3,720 EJ. .

KansasKansas

Heat flow in Kansas averages about 65 ± Heat flow in Kansas averages about 65 ± 9 mWm9 mWm-2-2 (n = 20). (n = 20).

The mean accessible The mean accessible LTITSLTITS resource resource base is base is 4,980 EJ4,980 EJ. .

Oklahoma and TexasOklahoma and TexasHeat flow averages 52 ± 22 mWmHeat flow averages 52 ± 22 mWm-2-2 (n = 11) in (n = 11) in Oklahoma and 62 ± 56 mWmOklahoma and 62 ± 56 mWm-2-2 (n = 50) in Texas. (n = 50) in Texas. The ORC power generation potential using The ORC power generation potential using waters from deep oil-producing formations in the waters from deep oil-producing formations in the Anadarko and Arkoma basins and Gulf Coast Anadarko and Arkoma basins and Gulf Coast regions ranges rom 1,124 to 5,393 MWe in regions ranges rom 1,124 to 5,393 MWe in Oklahoma and 1,094 to 5,252 MWe in Texas Oklahoma and 1,094 to 5,252 MWe in Texas (Blackwell, Negraru, and Richards, 2006). (Blackwell, Negraru, and Richards, 2006). This amount of energy is a thousand times This amount of energy is a thousand times greater than the annual electrical energy used in greater than the annual electrical energy used in the entire state of Texas. the entire state of Texas.

Technology AdvancesTechnology AdvancesUTC Power and Ormat have reverse engineered UTC Power and Ormat have reverse engineered industrial air conditioning systems (Organic Rankine industrial air conditioning systems (Organic Rankine Cycle - ORC) to create highly efficient turbine power Cycle - ORC) to create highly efficient turbine power generators. generators.

organic Rankine cycle binary organic Rankine cycle binary generatorsgenerators

According to UTC, the efficiency of the ORC According to UTC, the efficiency of the ORC system is such that 10 MW of heat can be system is such that 10 MW of heat can be converted practically into about 1 MW of converted practically into about 1 MW of electrical power.electrical power.

Water production at 1000 gpm at Water production at 1000 gpm at temperatures as low as 90 °C can be used to temperatures as low as 90 °C can be used to produce electricity at rates competitive with produce electricity at rates competitive with conventional power plants. conventional power plants.

UTC’s Pure Cycle-Model 200 provides 200 kW UTC’s Pure Cycle-Model 200 provides 200 kW using 165ºF using 165ºF water at water at 480 gpm480 gpm at Chena Hot at Chena Hot Springs Resort, Chena, AK. Electricity cost Springs Resort, Chena, AK. Electricity cost

dropped from 30¢ / kwh to 7¢ / kwh.dropped from 30¢ / kwh to 7¢ / kwh.

Co-produced Oil Field FluidsCo-produced Oil Field Fluids

The potential power production using oil field The potential power production using oil field waste waters with ORC technology is estimated waste waters with ORC technology is estimated to be at least 5.9 GW and could be as high as to be at least 5.9 GW and could be as high as 21.9 GW (McKenna et al., 2005; MIT - 2007). 21.9 GW (McKenna et al., 2005; MIT - 2007).

Requirements are: 1,000 gpm, for a well or a Requirements are: 1,000 gpm, for a well or a group of wells in relatively close proximity to group of wells in relatively close proximity to each other.each other.

Temperatures can be as low as 90 Temperatures can be as low as 90 ºC (192 ºF).ºC (192 ºF).

Opportunities for co-produced oil field Opportunities for co-produced oil field waterswaters

““Collecting and passing the fluid through a binary Collecting and passing the fluid through a binary system electrical power plant is a relatively system electrical power plant is a relatively straightforward process.”straightforward process.”““Piggy-backing on existing infrastructure should Piggy-backing on existing infrastructure should eliminate most of the need for expensive drilling eliminate most of the need for expensive drilling and hydrofracturing operations, thereby reducing and hydrofracturing operations, thereby reducing the risk and the majority of the upfront cost of the risk and the majority of the upfront cost of geothermal electrical power production.” geothermal electrical power production.”


Equivalent geothermal power from co-produced hot water associated with existing hydrocarbon production in the mid-continent.

StateState Total Water Total Water Produced Ann. Produced Ann.

in 1,000 kbblin 1,000 kbbl

Total Water Total Water Production Production Rate, kGPMRate, kGPM

Equivalent Equivalent Power,Power,MW @ 100MW @ 100ooCC



MontanaMontana 189,899 16 16 47 88

ColoradoColorado 487,331 44 44 112 212

North DakotaNorth Dakota 182,441 16 17 42 79

South DakotaSouth Dakota 6,725 1 1 2 3

NebraskaNebraska 102,005 9 9 23 44

KansasKansas 6,326,175 572 575 1,456 1,980

OklahomaOklahoma 12,423,264 1,124 1,129 2,860 5,393

TexasTexas 12,097,990 1,094 1,099 2,785 5,252

Total Mid-ContTotal Mid-Cont 31,944,930 2,876 2,890 7,327 13,051

TOTAL USATOTAL USA 50,527,333 4,590 4,591 11,631 21,933


Geothermal Energy Utilization Associated with

Oil & Gas Development Conference

June 12-13, 2007

http://www.smu.edu/geothermal/

http://www.smu.edu/geothermal/Oil&Gas/Geothermal_energy_utilization.htm

The Future ofGeothermal Energy The Future ofImpact of Enhanced GeothermalSystems (EGS) on the United Statesin the 21st Century

Massachusetts Institute of Technology

http://geothermal.inel.gov/

EGS Concept and Application







Excerpts from MIT Report on EGSExcerpts from MIT Report on EGS

““If we limit our calculation of stored thermal energy in If we limit our calculation of stored thermal energy in place to a depth of 10 km beneath the land area of place to a depth of 10 km beneath the land area of the United States, then the amount of thermal energy the United States, then the amount of thermal energy in the crust is so large (about 14 million quads) that in the crust is so large (about 14 million quads) that we can view it as sustainable (see Chapter 2, Table we can view it as sustainable (see Chapter 2, Table A.2.1).”A.2.1).”

““Even if we were to use it to provide all the primary Even if we were to use it to provide all the primary energy consumed in the United States, we still would energy consumed in the United States, we still would be depleting only a tiny fraction of it.”be depleting only a tiny fraction of it.”

Estimated U.S. geothermal resource base to 10 km depth by category

Category of ResourceCategory of Resource Thermal Energy, inThermal Energy, inExajoules (1EJ = 10Exajoules (1EJ = 1018 18

J)J)

Reference Reference

Conduction-dominated Conduction-dominated EGSEGS

Sedimentary rock Sedimentary rock formationsformations

100,000* may be 100,000* may be 400,000400,000

MIT - 2007 MIT - 2007

Crystalline basement Crystalline basement rock formations rock formations

13,300,000 13,300,000

MIT - 2007 MIT - 2007

Supercritical Volcanic Supercritical Volcanic

EGSEGS** 74,10074,100

USGS Circular 790USGS Circular 790

HydrothermalHydrothermal2,400 – 9,6002,400 – 9,600

USGS Circulars 726 USGS Circulars 726 and 790and 790

Coproduced fluidsCoproduced fluids 0.0944 0.0944 –– 0.4510 0.4510 McKenna, et al. (2005)McKenna, et al. (2005)

Geopressured systemsGeopressured systems 71,000 – 170,00071,000 – 170,000****

USGS Circulars 726 USGS Circulars 726 and 790and 790

* Excludes Yellowstone National Park and Hawaii** Includes methane content


SummarySummaryGeothermal energy is an underestimated and Geothermal energy is an underestimated and largely untapped resource that could have a largely untapped resource that could have a significant impact on the world’s energy future.significant impact on the world’s energy future.The LTITS resource base was underestimated by 400 percent.Advances in ORC technology make LTITS an electric power resource.The energy needed to produce an oil field can be generated from the heat contained in the waste water from the field.The combination of LTITS, hydrothermal, GHP, The combination of LTITS, hydrothermal, GHP, and EGS constitutes a sustainable resource that and EGS constitutes a sustainable resource that can provide all United States electrical power can provide all United States electrical power needs.needs.

Documents

A New Look at Geothermal Energy as an Energy Choice for the Future