how egs is investigated in the case of the larderello geothermal field ? guido cappetti
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How EGS is investigated in the case of the Larderello geothermal field ? Guido Cappetti Enel – Generation and Energy Management – Geothermal Production Engine Launching Conference Orleans 12-15 February 2006. Contents. The first exploitation period of Larderello - PowerPoint PPT PresentationTRANSCRIPT
How EGS is investigated in the case of the
Larderello geothermal field ?
Guido CappettiEnel – Generation and Energy Management – Geothermal Production
Engine Launching Conference
Orleans 12-15 February 2006
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Contents
The first exploitation period of Larderello
The Research&Development programs, from mid ’70s:
Deep exploration
Reinjection
Stimulation jobs
The reassessment of the geothermal resource
New exploitation strategies
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M. AMIATA
LARDERELLO
Temperature distribution at 3000m depth, in Italy
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Geothermal power growth up to 80’s
In 1913, at Larderello, first unit in operation (250 kW).
Italy was the sole country in the world for electricity generation from geothermal resources up to 1958, when a unit was installed at Wairakey (New Zealand).
Development of shallow reservoirs of Larderello, Travale/Radicondoli and Amiata.
Beginning of 70’s serious production decline problems
Oil crisis induced a renewal of interest towards geothermal energy and new R&D were implemented.
1904
•1904 First test in Larderello
•1913 First 250 kW unit in Larderello
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Top of the shallow Carbonate Reservoir
Temperature distribution in the Larderello area
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The problem of production sustainability was evidenced in the mid-‘70s, when the boundaries of the productive areas related to the shallow reservoirs were reached. The following R&D activities were
planned to sustain production.
The production sustainability
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Deep exploration 3000-4000 m
Reinjection / Injection
Stimulation of low productivity wells
Deep exploration 3000-4000 m
Reinjection / Injection
Stimulation of low productivity wells
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Deep exploration and development
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Top of the shallow Carbonate Reservoir
Temperature distribution in the Larderello area
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Conceptual model of the Larderello Geothermal field
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Temperature distribution at 3000 m b.s.l.
Temperature distribution in the Larderello area
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Reinjection
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Intensive exploitation of the Larderello-Valle Secolo area has gradually
depleted the fluid inside the reservoir .
Intensive exploitation: field depletion
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The reinjection has increased the steam production of about 100 kg/s, equivalent to 50 MW.
The long reinjection period has not substantially modified the temperature of the produced fluid.
Reinjection results
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The boiling of injected water produced additional steam devoid of gas which diluted the primary steam and therefore allowed a reduction of the weighted average gas content, with considerable energy savings for gas extraction from the power plant condensers.
Reinjection results
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Stimulation activities/EGS
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Injection of acid mixture (HCl and HF) and water produces self-propping effects in the fractures:
Microslippage of the fracture faces
Removal of cuttings and mud deposition inside the fractures
Acid leaching of hydrothermal mineralizations present in the fractures
Contraction and consequent cracking of hot rock formations due to thermal stress
Stimulation methodologies
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Acid attack Lab Acid attack Lab TestsTests
Aim: Selection of the best acid mixtures for the acid attack of rock matrices and hydrothermal mineralisations of deep geothermal reservoirs
Tested rock samples : Phyllites, micaschists, hornfels,and granites with some fractures filled with siliceous hydrothermal mineralizations (epidotes + K feldspar and chlorides + K feldspar + pyrites)
Tested acid mixture : HCl + HF, at different HCl/HF ratios
The tests have been carried out by the Enel-Lab and by the Lab of Pisa University - Department of Earth Sciences
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Acid attack Lab Acid attack Lab TestsTestsTests at batch conditions:
•temperatures in the range 100 - 150 °C
•two hours reaction time with an acid/rock ratio = 3 cm³/g
Tests in flowing conditions:
•temperatures of 30°, 50°, 70° 90 °C
•reaction time = 30’
Tested acid mixture:
9% Hcl - 1% HF; 6% Hcl - 6% HF; 6% Hcl - 3% HF; 12% Hcl - 6% HF;
12% Hcl - 3% HF
Performed analyses :
- weight of dissolved solids
- chemical analyses of reactions products
- mineralogic analyses of the leached rock surface by electronic microscope and X ray
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Equipment for Lab Equipment for Lab teststests
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Lab Lab teststests
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Lab Lab teststests
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Field Field teststests Well Bagnore_25: 3397 m bottom hole. Phyllites: fractured zone near the
well bottom. Acid job: injectivity improved from 3 to 15 m³/h/bar
Well Radicondoli_29: 4826 m bottom hole - hornfels rocks and granite from 4230 mInjectivity improved from 1 to 7 m³/h/bar
Well Montieri_4: granite from 2000 to 3721 m (bottom hole), characterized by high hydrothermal alterations, temperatures of about 300 °C and low permeability.Injectivity improved from 0.4 to 5 m³/h/barThe well can produce 50 t/h of steam (6.5 MW)
Well Travale Sud_1: 2987 m bottom hole - hornfels rocks Acid job: productivity increased from 30 to 110 t/h (about 15 MW)
Well Montieri_1: 2219 m bottom hole - hornfels rocks. Acid job with 200 m³ of 12% HCl - 6% HF. Injectivity improved from 3 to 15 m³/h/barThe well is now producing about 250 t/h of steam (~35 MW)
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Improvement of well production characteristics by the injection of cold water
Field tests
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The deep drilling activity pointed out the presence of productive layers up to depths of 3000-4000m, in a very wide area
The reinjection/injection strategies proved to be successful for sustaining/increasing the fluid production
The stimulation jobs are applied successfully to increase the wells productivity
Reassessment of the geothermal resources has been carried out and new exploitation strategies have been adopted, based on:
Heat Production
Production Sustainability
The results of the R&D in Italy
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Larderello/Travale Steam production history
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Steam flow-rate
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Power development
Positive results of deep drillings, stimulations and reinjection
12 new units (314,5 MW) started up in the period 2000-2005
8 units, for a total of 214.5 MW, replaced old units in operation from many years and considered “obsolete”. The new units are characterised by higher efficiency and lower environmental impact.
4 units, for a total of 100 MW are new capacity installed both in marginal and central areas
Nuova Larderell
o(20 MW)
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Electricity generation and steam flow-rate in the Larderello geothermal field
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USA: The Geyser production trend
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Evolution of the exploitation strategies
From hydrothermal systems...
Fractured reservoirs with high permeability and fluids inside
… to Hot Dry Rocks Tight formations with high temperatures
Heat Production
Heat Production
Production of the stored fluids analysis of the field depletion
Hydraulic stimulation for the creation of an artificial fracture network
Stimulation jobs and secondary heat recovery through water reinjection/injection
Water circulation for the heat extraction
Enhanced Geothermal SystemsEnhanced Geothermal Systems
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What does it means to enhance a geothermal system ?
-to improve the knowledge of the system-to enhance the permeability of the formation-to enhance the heat production through water circulation
To enhance fluid production and electricity generation
Considerations about Considerations about EGSEGS
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ConclusioConclusionsns
• Larderello has been the first geothermal system developed and exploited in the world (over 100 years history…)
• First period of intensive explotation with “conventional” strategies, typical of hydrothermal systems
• Now Larderello can be considered the largest worldwide example of an Enhanced Geothermal System
• The exploitation strategies are based on the “Heat Production” and are aimed at the “Production Sustainability”
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Thanks for your attention!Thanks for your attention!