geothermal energy for sustainable development: recent ... · geothermal energy for sustainable...

Geothermal energy for sustainable development: recent advances in

exploration and exploitation of resources

Michele Pipan, University of Trieste Exploration Geophysics Group

Sustainable Energy: Challenges and Opportunities International Conference on Science, Arts and Culture

Veli Lošinj, Croatia, 23-27 August 2010 1

Acknowledgment

ECSAC 2010 - Veli Lošinj, Croatia, 23-27 August 2010 2

This presentation gives an update of current situation and perspectives of geothermal energy, as well as

state-of-the-art and new developments in the field of geothermal science and technology.

Statistical data and part of the images are based on the

following sources:

• IGA (International Geothermal Association) working group for the 2008 IPCC geothermal panel;

• IEA (International Energy Agency); • GRC (Geothermal Resources Council); • EIA (U.S. Energy Information Administration); • EERE (U.S. Energy Dept., Energy Efficiency &

Renewable Energy); • GEA (Geothermal Energy Association) • GEO (Geothermal Education Office)

Rationale

INNOVATIVE TECHNIQUES CAN OPEN NEW

FRONTIERS FOR THE UTILIZATION OF GREATER

FRACTIONS OF THE IMMENSE AND LARGELY

UNTAPPED THERMAL ENERGY OF THE EARTH

3 ECSAC 2010 - Veli Lošinj, Croatia, 23-27 August 2010

Summary

• GEOTHERMAL ENERGY: o What is? o Where can be found? o Current status of exploration/exploitation

• WORLD STATUS AND GLOBAL GROWTH SCENARIOS • PERSPECTIVES, CHALLENGES, NEW TECHNOLOGIES:

o Exploration: advanced geophysical imaging and reservoir characterization/monitoring

o Drilling o EGS o Supercritical fluid o Others

• CONCLUSIONS


MAIN HEAT SOURCE: Decay of long-lived radioactive isotopes of uranium (U238, U235), thorium (Th232) and potassium (K40) HEAT BALANCE:


Geothermal energy

Source % total volume

Heat flow (W)

Crust 2 8x1012

Mantle 82 32.3x1012

Core 16 1.7x1012

Total 42x1012

TOTAL HEAT CONTENT OF THE EARTH (reckoned above an average surface temperature of 15 °C):

≈ 12.6 x 1024 MJ HEAT CONTENT OF THE CRUST:

≈ 5.4 x 1021 MJ

BUT…


Geothermal energy

… ONLY A FRACTION CAN BE UTILIZED TO DATE, DEPENDING ON FAVOURABLE GEOLOGICAL CONDITIONS…


Geothermal energy


Geothermal energy

…I.E. CARRIER AVAILABLE TO TRANSFER HEAT FROM DEEP HOT ZONES TO THE SURFACE

INNOVATIVE TECHNIQUES MAY OPEN NEW FRONTIERS IN THE NEAR FUTURE…


Geothermal energy

… AND ALLOW UTILIZATION OF LARGER FRACTIONS OF THE UNTAPPED RESOURCES


Geothermal energy


Geothermal energy

The heat in place is not the question. The question is: how much can be taken out and at what price.

Nobody knows the answer, although the resource is immense.

SCHEMATIC REPRESENTATION OF A GEOTHERMAL SYSTEM


Geothermal energy

MODEL OF THE GEOTHERMAL SYSTEM


Geothermal energy

CLASSIFICATION OF GEOTHERMAL RESOURCES


Geothermal energy

RESOURCES TEMPERATURE (°C)

1978 2000

Low enthalpy < 90 <125 <100 ≤150 ≤190

Intermediate enthalpy 90-150 125-225

100-200

- -

High enthalpy >150 >225 >200 >150 >190


Geothermal energy

GEOTHERMAL ENERGY USES


Geothermal energy

GEOTHERMAL ENERGY USES


Geothermal energy

• Electric power generation

• Direct use

• Heat pumps


Flash steam power plants tap into reservoirs of water with

temperatures greater than 182ºC. As it flows, the fluid pressure

decreases and some of the hot water boils or "flashes" into steam. The steam is then separated at the

surface and is used to power a turbine/generator unit

Flash steam power plants

Dry steam plants use hydrothermal fluids that are primarily steam. The steam goes

directly to a turbine, which drives a generator that produces electricity.

Dry steam power plants

Binary cycle power plants operate on water at lower

temperatures of about 107-182ºC. These plants use the heat from the geothermal water to boil a working fluid, usually an organic compound

with a low boiling point.

Binary cycle power plants

Global Installed capacity 2007

Units

Capacity （GW)

58

2.6

237

0.8

Highly cost competitive but geographically limited

Most dominant in terms of global capacity

Useful alongside geothermal heating, hot springs, etc

195

5.6

Average size （MW)

~45 ~29 ~3

ELECTRIC POWER: conventional technologies


ELECTRIC POWER: current perspective and future outlook

– Capex of conventional technologies are expected to decrease in the long term, driven by a significant reduction in drilling costs resulting from adoption of new technologies. Evolution of margin of drilling players is unclear in the long term because very dependent on oil industry dynamics

– Outlook of future demand appears moderately positive, driven by increasing development focus of high potential countries; significant untapped potential; stable development of low-enthalpy binary technology

– Enhanced geothermal systems (EGS), still in an early stage of development, might represent a breakthrough technology in the long term (not before the next 10 years, if issues of seismic implications and replicability are addressed) given that it is not subject to the same geographic constraints of conventional technologies (i.e., could be technically developed everywhere)

Future outlook

2

Current perspective

1

– Three “conventional” geothermal technologies, according to a site’s geological attributes: dry steam (~3 GW of installed capacity), flash steam (~6 GW of installed capacity), binary cycle (~1 GW of installed capacity)

– Economics of conventional geothermal technologies, although very site specific, are typically attractive vs. other renewables

– Growth of installed capacity has been slow (3% p.a.), constrained by long lead time, geographic concentration of natural potential, and specific development competences required

– Industry profile is mainly local (only few players at “regional” level) and highly fragmented. While different business models will coexist, first indications of a possible industry paradigm shift towards vertical integration and global presence are emerging


WORLD STATUS AND GROWTH SCENARIO



An increase of about 800 MW in the three year term 2005-2007 has been

achieved, following the rough standard linear trend of

approximately 200/250 MW per year

The geothermal electricity installed capacity is approaching

the 10,000 MW threshold, which can be reached by end

2010

Installed Capacity Wordlwide

0

2

4

6

8

10

12

1970 1980 1990 2000 2010Year

Ca

pa

cit

y G

W



9,69,3

8,98,68,48,17,9

6,8

5,8

3,9

0,8

1970 1980 1990 1995 2000 2001 2002 2003 2004 2005 2006

+3%

Installed capacity in GWe



Comparison with other RES: Wind power, existing World Capacity, 1996-2008



Comparison with other RES: Solar PV, existing World Capacity, 1995-2008



Comparison with other RES: Solar PV and Geothermal Power growth, 1995-2008

Installed Capacity Wordlwide

0

2

4

6

8

10

12

1970 1980 1990 2000 2010Year

Ca

pa

cit

y G

W

Geothermal



Electricity production from RES in 2008*

*) Source: installed capacity from the REN21 report,

capacity factors from Fridleifsson et al. (2008)

Fridleifsson, I.B., R. Bertani, E. Huenges, J. W. Lund, A. Ragnarsson, and L. Rybach (2008): The possible role and contribution of geothermal energy to the mitigation of climate change. In: O. Hohmeyer and T. Trittin (Eds.) IPCC Scoping Meeting on Renewable Energy Sources, Proceedings, Luebeck, Germany, 20-25 January 2008, 59-80.

Renewables – Global Status Report 2009. REN21 (Renewable Energy Policy Network for the 21st Century)

Technology Installed capacity by mid 2008 (Gwe)

Capacity factor (%) Electricity produced (TWh)

Wind 121 21 222.6

Solar PV 13 14 15.9

Geothermal 10 75 65.7



WORLD FORECASTING

Difficult to estimate the overall world-wide potential,

due to too many uncertainties. Nevertheless, it is possible to identify a

range of estimations, taking into account new technologies:

• permeability enhancements • drilling improvements • enhanced geothermal system • low temperature production • supercritical fluid

Standard: 70 GW Improved: 140 GW

It is possible to produce up

8.3% of total world electricity production, serving 17% of world population.

39 countries (located mostly in

Africa, Central/South America, Pacific) can be 100% geothermal powered.

29

GEOTHERMAL

ECSAC 2010 - Veli Lošinj, Croatia, 23-27 August 2010



Energy and Investment costs for electricity production from RES *

*) Source: World Energy Assessment Report, UNDP/UN-DESA/World Energy Council, 2000

Technology Current energy cost (USc/kWh)

Potential future energy cost (USc/kWh)

Turnkey investment cost (USD/kW)

Biomass 5-15 4-10 900-3000

Geothermal 2-10 1-8 800-3000

Wind 5-13 3-10 1100-1700

Solar PV 25-125 5-25 5000-10000

Solar CSP 12-18 4-10 3000-4000

Tidal 8-15 8-15 1700-2500



GLOBAL GROWTH SCENARIO

Projection of geothermal power development (left); projection of direct use heat production (right) to 2050. From Fridleifsson et al. (2008).

How to achieve this growth? >> EGS chances and challenges <<

0

40

80

120

160

1990 2000 2010 2020 2030 2040 2050

Ca

pa

cit

y (

GW

)

0

400

800

1200

1600

Ele

ctr

icit

y p

ro

du

cti

on

(T

Wh

/yr)

GW TWh/yr

0

1'000'000

2'000'000

3'000'000

4'000'000

5'000'000

6'000'000

2000 2010 2020 2030 2040 2050 2060

TJ

/yr

Total

Geothermal Heat Pumps (GHP)

Direct Use other than GHP


PERSPECTIVES, CHALLENGES, NEW TECHNOLOGIES

Enhanced Geothermal Systems (EGS): Basic scheme for heat/power co-generation

The key component:

an extended, sufficiently

permeable fracture

network at several km

depth, with suitable heat

exchange surfaces.

~200°C



The EGS principle is simple: in the deep subsurface

where temperatures are high enough for power

generation (150-200 °C) an extended fracture network is

created and/or enlarged to act as new fluid pathways.

Water from the surface is circulated through this deep

heat exchanger using injection and production wells, and

recovered as steam/hot water.

Further surface installations complete the circulation

system. The extracted heat can be used for district

heating and/or for power generation.



Soultz-sous-Forêts – Rhein graben EGS project – “Heat Mining”

1.5 + 4.5 MWe

geophone geophone

production 50 kg/s

production 50 kg/s

600 m 200oC depth 5000 m 600 m

GPK2 GPK3 GPK4

Observation well Observation well

Injection 100 kg/s

1400 m

European Economic Interest Group 4 countries including ENEL Commercial electricity production •Inject cold water at 5 km •Obtain 200°C water/steam •Produce 6 MWe by 2007

Suitable European sites potential = 110 000 MWe



EGS is the future!

M.I.T. study (2006) 358 p.



The M.I.T. study “The Future of Geothermal Energy” (2006) determined recoverable resources > 200,000 EJ alone for the USA, corresponding to 2,000 times the annual primary energy demand. To universally utilize these immense resources exciting R&D problems need to be tackled:

High-Resolution 3-D/4-D imaging, characterization and monitoring of geothermal reservoir and subsurface conditions

Development of a technology to produce electricity and/or heat from a basically ubiquitous resource, independent of site conditions (“EGS technology”).



…R&D CHALLENGES IN EGS DEVELOPMENT (cont.):

Acquiring experience about possible changes of an EGS heat exchanger with time

To see whether and how the EGS power plant capacity could be upscaled from the currently few MWe to several 10 – 100 MWe

ECONOMIC FEASIBILITY VS. GEOLOGIC ASSURANCE


The role of innovative geophysical techniques



EUR million, based on a 20 MW plant

Capital cost per MW ranging between 4 and 6 million EUR

30

1-2

Site scouting and geophysical

exploration

20-30

Exploratory drilling

Drilling

50-60

Field development

30-60

Power plant construction

80-120

Total expenses

– Upfront costs for exploration

– Exposure to risk of failure (i.e., site not sufficiently attractive for development)

CAPEX IMPLICATIONS


ECONOMIC/POLICY WARNING

“…To a great extent, energy markets and government policies will influence the private sector’s interest in developing EGS technology. In today’s economic climate, there is reluctance for private industry to invest its funds without strong guarantees. Thus, initially, it is likely that government will have to fully support EGS fieldwork and supporting R&D. Later, as field sites are established and proven, the private sector will assume a greater role in cofunding projects – especially with government incentives accelerating the transition to independently financed EGS projects in the private sector. Our analysis indicates that, after a few EGS plants at several sites are built and operating, the technology will improve to a point where development costs and risks would diminish significantly, allowing the levelized cost of producing EGS electricity in the United States to be at or below market prices…” (From M.I.T. report, “The Future of Geothermal Energy”, 2006)



The Regional scale



The Regional 2-D cross-section and subsurface model



The Regional 2-D cross-section and …



…The Regional subsurface model

46


The Site Scale: 3-D High-Resolution imaging and characterization


47



The Site Scale: 3-D High-Resolution imaging and characterization

Fractures



The Reservoir scale…



The Petrophysical characterization

50


REMARKS


• 3-D seismic imaging is a powerful tool to:

o unravel complex structural features

o identify faults and fractures with adequate precision for exploratory/production drilling purposes

o obtain detailed 3-D structural models of use in the identification and assessment of geothermal resources

NONETHELESS…

51


REMARKS


• Seismic data are sensitive to acoustic impedance contrasts • Different types of fluids and/or variations of temperature may

have little effect on acoustic impedance • Even seismic AVO response and instantaneous seismic

attributes do not allow convincing discrimination between fluid/lithology variations

THEREFORE…

52


REMARKS


The road ahead in geothermal exploration: Joint Seismic/EM imaging and inversion Example of fluid saturation imaging from joint EM and SEISMICS



IMAGING AND CHARACTERIZATION OF DEEP GEOTHERMAL RESERVOIRS

Combined results of resistivity soundings (TEM/MT ) and micro-seismicity analysis at the Krafla geothermal field (Iceland)

Pre-drilling exploration

results:

Resistivity shows a conductive body at average 4-5 km depth but with pinnacles up to 2km.

• Micro-earthquakes show that seismicity occurs above the conductive body indicating T higher than 700°C

Drilling results:

• A borehole pointing towards a pinnacle hit acidic magma at 2,1 km



…BACK TO THE EGS CHALLENGE>> LONG-TERM BEHAVIOUR?

There is no experience about possible changes of an EGS heat exchanger with time.

Permeability enhancement (e.g. new fractures generated by cooling cracks, mineral dissolution) could increase the recovery factor,

while permeability reduction (e.g. by mineral deposition) or short-circuiting could reduce recovery. Without having field-scale experience with long-term EGS production the economic estimates about production, and maintenance costs remain unsubstantiated.



OTHER RD SECTORS: DRILLING Comparison of drilling costs (indexed) to crude oil and natural gas prices

–Historically, significant correlation between drilling cost and crude oil prices

–Current scenario of low crude oil prices, offers attractive opportunities to:

•Scale up drilling plans

•Investigate partnerships with drilling players at attractive conditions

– Higher crude oil prices resulted in increased oil and gas exploration and drilling activity, leading to shortage of drilling rig

– By simple supply-demand dynamics, shortage led to an increase in costs of rig rental and drilling equipments



OTHER RD SECTORS: DRILLING Current oil/gas drilling technologies

adaptable to geothermal Revolutionary new drilling techniques

– Expandable tubular casings: Shell technology which allows for in situ plastic deformation of tubular casing

– Under-reamers: provides cementing clearance for casing strings

– Low clearance casing design: accepts lower clearance to use expandable tubulars (under-reamer may be required)

– Drilling with casing: permits longer casing intervals and thus results in fewer strings

– Multilateral completions/stimulating through sidetracks and laterals: sequentially stimulation of geothermal reservoirs

– Well-design variations: extended length of casing intervals will reduce number of casing strings

– Projectile drilling: projecting steel balls at high velocity using pressurized water to fracture and remove the rock

– Spallation drilling: uses high-temperature flames to rapidly heat rock surface and causing it to fracture

– Laser drilling: uses laser pulses to rapidly heat rock surface and causing it to fracture

– Chemical drilling: involves use of strong acids to break down the rock; may be used in conjunction with conventional drilling techniques

– Impact of adaptation of current drilling technologies may be less significant than lower drilling cost driven by oil sector dynamics

– Effect of revolutionary drilling could instead by significant



OTHER RD SECTORS: SUPERCRITICAL FLUIDS

3,5 km Minimum Casing depth

4 - 5 km Target depth

Its aim is to produce electricity

from natural supercritical fluids from

drillable depths.



OTHER RD SECTORS: SUPERCRITICAL FLUIDS The current plan is to drill and test at least three 3.5-5 km deep boreholes in

Iceland within the next few years (one in each of the Krafla, Hengill, and Reykjanes high-temperature geothermal systems). Beneath these three developed drill fields temperatures should exceed 550-650°C, and the occurrence of frequent seismic activity below 5 km, indicates that the rocks are brittle and therefore likely to be

permeable. Modelling indicates that if the wellhead enthalpy is to exceed that of conventionally produced geothermal steam, the reservoir temperature must be

higher than 450°C.

A deep well producing 2500 m3/h of steam from a reservoir with a temperature significantly above 450°C could yield enough high-enthalpy steam to generate

40-50 MW of electric power. This exceeds by an order of magnitude the power typically obtained from

conventional geothermal wells. This would mean that much more energy could be obtained from presently exploited high-temperature geothermal fields from a

smaller number of wells.



NEW TECHNOLOGIES

• Resource Identification (science): new geological and geophysical methods will lead to cost and risk reduction

• Power conversion technology (technology): improving heat-transfer

performance for low temperature fluid, developing plant design with high efficiency and low parasitic losses. It will increase the available

resource basis to the huge low-temperature regions, not bounded to the plate boundary (binary plants technology)

• Reservoir (science & technology): increasing production flow rate by

targeting specific zones for stimulation and improving downhole lift systems for higher temperature, improving heat-removal efficiency in

fractured rock system. It will lead to an immediate cost reduction increasing the output per well and extending reservoir operating life.

• IN THE FUTURE >> EGS!!!


CONCLUSIONS

Geothermal is well positioned within the Renewables Wind and solar PV power growth leaves geothermal behind Substantial geothermal growth could be provided by EGS Still many problems need to be solved in EGS There is a great need for R & D


CONCLUSIONS (2)

• Advanced exploration methods are crucial to reduce risks of failure in geothermal drilling and relevant costs in the exploratory phase

• Exploration strategies must be tailored for each geothermal field

• The most promising methods include combined use of resistivity and active/passive seismic methods


CONCLUSIONS (3)

• Advanced geophysical methods can further support and help optimizing the development/production phase through high-resolution characterization and monitoring of the geothermal system

• A large and targeted research effort is needed to improve the geothermal exploration methods


CONCLUSIONS (4)

•Total geothermal electricity is reaching the value of 9,7 GW in 24 countries, with 800 MW of increase since 2005; the forecasting for 2010 is about 11 GW •Geothermal energy is not widely diffuse, but its base-load capability and its high availability are key elements for its penetration into the energy market •Binary plant technology is playing a very important role in the modern geothermal electricity market •The possibility of production from Enhanced Geothermal Systems (EGS) (to be considered as a possible future developments) can expand its availability on a worldwide basis

The maximum reduction of CO2 will be 1000-500 million of tons for electricity

and 200 million tons for direct utilizations


EVENTUALLY…

Many thanks for your attention !

Prof. Michele Pipan

University of Trieste

Department of Geosciences

34127 Trieste - Italy

[email protected]

ECSAC 2010 - Veli Lošinj, Croatia, 23-27 August 2010 65

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