h. traineau, b. herbrich, e. lasne, d. tournaye

Geothermal Development in the Caribbean and EGS Perspectives

ENGINE Launching Conference – Orléans, Feb. 12th to 15th, 2006

H. Traineau, B. Herbrich, E. Lasne, D. Tournaye

CFG Services, 3 av. Cl. Guillemin 45064-Orléans cedex 2 – France

A. Genter, B. Sanjuan

BRGM, 3 av. Cl. Guillemin, 45060-Orléans cedex 2 - France

Geothermal Development in the Volcanic Caribbean Islands

and EGS Perspectives



Map of the Caribbean volcanic islands (red color) and their active

or recent volcanoes.

Subduction of the Atlantic Plate below the Caribbean Plate



Energy in the Caribbean

- More than 90% of electricity comes from fossils fuels;

- Low contribution of Renewable energy sources :

- Electricity needs increase by 4-5% every year.

- Biomass- Hydro- Solar- Wind- Geothermal



Volcanic Islands

Survey Pre- feasibility

Deep drillings

Installed capacity (MWe)

Expected Potential (MWe)

Saba yes

St Eustatius yes

St Kitts yes

Nevis yes 10 - 50

Montserrat yes yes

Guadeloupe yes yes yes 15 30 - 50

Dominica yes yes 50 -100

Martinique yes yes yes

Ste Lucia yes yes yes 10 - 50

St Vincent yes yes

Grenada yes



Geothermal resources might contribute to power generation in some islands instead of fossil fuels

Bouillante, the case history in Caribbean

Dominica, the most promising geothermal potential



The Bouillante geothermal field, Guadeloupe

Urban areaSteep topography area

Sea proximity



The story of the Bouillante geothermal exploitation

1963 1969 1986 2001 2004

First survey(BRGM)

First drillings(EURAFREP)

First 4,5 MWe power plant

(EDF)

Second 11 MWe power plant

(GEOTHERMIE BOUILLANTE)

Drilling 3 new wells(GEOTHERMIE BOUILLANTE)



- Several recent eruptive centers (<1 MA) around the Bouillante Bay, with the possible occurrence of shallow magmatic intrusion under cooling;

- Several main normal faults which promote permeability and fluid circulations at depth and represent potential fractured reservoirs;

- Only a part of the reservoir is now exploited through BO-4 vertical production well, BO-5 and BO-6 deviated and inclined production wells which intersect the Cocagne Fault.

The Bouillante geothermal field

B o - 4

B o - 5

B o - 6

B o - 7

B o - 1

B o - 2B o - 3

C a r ib b e a n

S e a

BouillanteBay

( O ,84 M y )

( 1 ,12 M y )

( O ,6 M y )

( < O ,6 M y )

( N o da te )

( N o da te )

Main zoneof surface manifestations

Hot spring

Recent volcaniccenter (age M. y)

Exploratory well

Main fault zones

Cocagne F.

Descoudes F.

Marsolle F.

Machette F.

Bouillante

Inclined, deviatedproduction well

N

Muscade

Thomas

1 km

Pointeà Lézard



S eaw ate rIn filtra tion

F ra ctu re d reservo ir

R a in fa llIn filtra tion

2 5 0 °

500 m

1000 m

Simplified model of fluid circulations in the Bouillante geothermal reservoir

Simplified cross-section along a West-East profile within the Bouillante geothermal field showing the assumed model of fluid circulation with seawater and rainfall recharge, mixing (60% seawater + 40% rainfall) and heating to 250-270°C.



0

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60 80 100 120 140 160 180 200 220 240 2600

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ORKUSTOFNUN

COMPAGNIE FRANCAISE DE GEOTHERMIE

Bouillante Wells 2, 4, 5, 6 and 7

BO-2, 16-03-2002 staticBO-4, 15-03-2002 staticBO-5, 13-03-2002 staticBO-6, 14-03-2002 staticBO-7, 13-03-2002 static

Temperature (°C)

Dep

th(m

)

Selected temperature profiles in the Bouillante wells.

240°C at shallow level (well BO-2)

Reservoir temperature around 250°C



Cross-section along a NW-SE profile showing well trajectories, location and quality of permeable

zones in relation with faults deduced from surface geology.

- Only the Cocagne Fault appears to be highly permeable.

- Plateau Fault shows low permeability.

- Descoudes Fault has no permeability possibly due to carbonates scaling

1400

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BO-7

1400

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BO-6

1200

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BO-2

200

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-1400

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NW SE

Sea level

BO-4

CocagneFault

PlateauFault

DescoudesFault

Location of the main feed zone

High permeable productive zone

Low permeable productive zone

Thickcalcitevein



High temperature conditions at shallow depth (< 1000 m deep) but strong anisotropy in permeability related to fracture network and possibly to scaling (carbonates, silica).

Main characteristics of the 7 deep wells drilled at Bouillante

Well Year Trajectory Total length (m)

Bottom hole T (°C)

Result

BO-1 1969 vertical 850 (225) No HP production

BO-2 1970 vertical 350 245-250 Producer


BO-4 1974-77 vertical 2 500 250 Low producer(Stimulation needed)

BO-5 2001 deviated 1 197 250 Good producer


BO-7 2001 deviated 1 400 240 No HP production



High temperature conditions at shallow depth (< 1000 m deep) but strong anisotropy in permeability related to fracture network and possibly to scaling (carbonates, silica).

Main characteristic of the 7 deep wells drilled at Bouillante

Well Year Trajectory Total length (m)

Bottom hole T (°C)

Result


BO-2 1970 vertical 350 245-250 Producer


BO-4 1974-77 vertical 2 500 250 Low producer(Stimulation needed)



BO-7 2001 deviated 1 400 240 No HP production

Extension of EGS methods might be addressed first to accurate location of faults within the high temperature, fracture-permeable reservoir.



0 2 4 6 8 10 12 14 16 18 20 22 24

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ORKUSTOFNUNCOMPAGNIE FRANCAISE DE GEOTHERMIE

Calculated and Measured Production Characteristics of Well BO-4

Conditions at first production test in 1998 Conditions at second production test in 1998 Measured point during second test in 1998 Measured points in July 1999 Measured points in May 2000 Approximate characteristic curve

Tot

al P

rodu

ctio

n R

ate

(t/h

)

Wellhead Pressure (bar-g)

Stimulation of the low productive well BO-4

A limited, low cost experiment with cold

seawater injected into the well BO-4 has been

conducted from August 10 - 27, 1998 to enhance the

secondary permeability through thermal cracking.

Productivity increases by 50% and fluid discharge

is more stable.



0 2 4 6 8 10 12 14 16 18 20 22 24

0

20

40

60

80

100

120

140

160

ORKUSTOFNUNCOMPAGNIE FRANCAISE DE GEOTHERMIE

Calculated and Measured Production Characteristics of Well BO-4

Conditions at first production test in 1998 Conditions at second production test in 1998 Measured point during second test in 1998 Measured points in July 1999 Measured points in May 2000 Approximate characteristic curve

Tot

al P

rodu

ctio

n R

ate

(t/h

)

Wellhead Pressure (bar-g)

Stimulation of the low productive well BO-4

A limited, low cost experiment with cold

seawater injected into the well in steps has been

conducted from August 10 - 27, 1998 to enhance the

secondary permeability through thermal cracking.

Productivity increases by 50% and fluid discharge

is more stable.

Extension of EGS methods could be very useful to improve permeability of low producers.



The location of the plant within the city induced strong environmental constraints (no noise, no steam plume, …).

Aerial view of the geothermal plant located within the city

Bouillante 1 Unit(4,5 MWe)

Bouillante 2 Unit(11 MWe)



Steep topography and urban area reduce land availability for well pads, pipe routes, etc…, and consequently may hinder best locations for production and reinjection zones.

Aerial view of the well pad and the pipe route.



Sea proximity also reduces surface availability for well siting and might require to reduce distances between production and reinjection zones.

Bouillante



Sea proximity also reduces surface availability for well siting and might require to reduce distances between production and reinjection zones.

Extension of EGS methods could be very useful to improve and secure reservoir monitoring and exploitation (tracer tests, …)

Bouillante



Dominica Island

Two promising high enthalpy geothermal fields with abundant surface manifestations, related to very recent volcanic activity.

Wotten Waven

Soufriere

Valley of Desolation



Dominica Island

Development of geothermal resources in Dominica and reservoir exploitation will face similar problems as experienced in Guadeloupe (remote location, steep topography, national park, …)

Valley of Desolation

Micotrin lava domeWotten Waven



Conceptual model of the Wotten Waven geothermal reservoir(s) with inferred location of deep chloride reservoirs and fluid flow pattern.



Permeability within the basement is provided by fault networks. Faults will be the main targets for well siting.

Rose diagram of fractures recorded on the field



Volcanic islands in the Caribbean have proved or expected high enthalpy geothermal resources which could be used for electricity production.

Due to their location, Bouillante and other fields (will) have to face problems related to :

- Permeability anisotropy within the geothermal reservoir; wells have to intersect main faults in order to be good producers;

- Steep topography and limited land availability for well pad, pipe routes,…;

- Environmental constraints due to urban areas or national park;

- Remote location (extra costs for survey, drilling, logging, stimulation and work over operations, plant maintenance,…);

- Limited size of the exploitation and limited financial capacity of geothermal operators;

CONCLUSIONS



Some problems could be addressed by EGS methods to promote development of their geothermal resources :

- Accurate location of fault network;

- Permeability improvement through well stimulation;

- Reservoir monitoring (tracer tests, logging);

- Management of close production and reinjection zone;

- ….

EGS PERSPECTIVES

h. traineau, b. herbrich, e. lasne, d. tournaye

Documents

bouillante wells

reservoir temperature

deep wells

low permeability

good producerbo72001deviated1

good producerbo62001deviated1

fossil fuels bouillante

fracturepermeable reservoir