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Application of Seismic Methods inLarderello – Travale Geothermal Fields             Tuscany, Italy              Presented ...
Outline•   Introduction on geothermal systems•   Geophysical methods•   Seismic Methods•   Larderello – Travale geothermal...
IntroductionRECHARGEAREAPERMEABLE FLOWPATH                    CONVECTION FLOW                    HEAT SOURCE              ...
http://geothermal.marin.org                              4
http://geothermal.marin.org   5
Geophysical Methods Include :  • Thermal surveys : T gradients, T distribution, heat flow  • Resistivity : to delineate f...
Seismic Methods Passive Methods :  •   It can be natural or induced by geothermal activity  •   Micro Seismic Survey, can...
Larderello – Travale Geothermal fields                                    •   Area of deep field 400km2                   ...
Seismic Data                                           9               (From Cameli et al, 2000)
Stacked data – seismic line LAR 36                                                                  • Decrease in coeffici...
Migrated data from seismic line LAR 36                            with projection of 2 directional wells                  ...
Methodology   Theoretical    • Studies the cause and the effect relationship between interesting      petrophysical relat...
THEORITICAL STUDY         • Large velocity and density         reduction at fractured production         level (3710m)3710...
THEORITICAL STUDY - AVO RESPONSE• As shear velocity data unavailable, theAVO response computed with “what if ”procedure   ...
Data for empirical study – VSP within the metamorphic basement(From Cameli et al, 2000)                                   ...
EMPIRICAL-STATISTICAL STUDYType of data :►   Fracture data (from prod. Wells)     • Producing zones PF     • Scarcely prod...
Empirical-Statistical study•   73% of seismic reflections correspond to fractured zones,    being the depth deviation less...
Conclusions•   The empirical study show that, within the Larderello-    Travale deep reservoir, 73% of the seismic reflect...
Conclusions•   Seismic reflection method has played an important role    for identification of deep geothermal targets in ...
Current status of the Fieldhas been producing since 1960swith 790 MW capacity fromtotal 32 geothermal power plants,providi...
References► Primary sources :   o Bertani, R., Bertini, G., Cappetti, G., Fiordelisi, A., Marocco, B.M., 2005, An      Upd...
Thank you      andAny Questions ???                    22
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Seismic method in italy

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  • This is more less the outline of my presentation. Firstly in the first 2 minutes, I will give some background about geothermal system, intro on geophysical methods applied before bringing you to the main topic of seismic application in Larderello Travale geothermal. At the end, I will give you chance to throw some questions.
  • A cartoon that may give you a better idea about geothermal reservoir with its key elements . When the rising hot water and steam is trapped in permeable and porous rock under a layer of impermeable rock it can form a geothermal reservoir
  • Geologic/tectonic setting controlling the occurrence of geothermal system which are mainly concentrated in circum pacific ring of fire, spreading centres, continental rift zones and hot spots of volcanisms are located, rift zones and mantle plumes area, where mostly high heat flow conditions are found as important key element in geothermal system.
  • Typical manifestations of the geothermal activity at the surface, especially when the cap rock is absent.
  • Key point of the geophysical application in geothermal is defining anomalies as resulted by geothermal process involving water rock interaction below the surface. However choosing the effective method really depends on target to define which will be different for ach prospect and significantly based on its accessibility. Geothermal fields are commonly in rough terrains, mountainous. In such terrain, dipole-dipole traversing resistivity or airborne magnetic etc. will be much more effective.
  • Seismic refraction surveys have been used to a limited extent because of the amount of effort required to obtain refraction profiles giving information at depths of 5 to 10 km, and the problems caused by the generally high degree of complexity of geological structures in areas likely to host geothermal systems. Seismic reflection – widely applied, with surprisingly valuable contribution in detecting fracture, regional structure, monitoring. However, seismic method is relatively expensive, as it may cost a test well. Besides, analysing seismic data is much more challenging than in oil as large velocity contrast due to hydrothermal process also variety of the rock hosting the reservoir.
  • These fields have been producing since 1960s. I chose the fields, as seismic methods have been intensively applied in last 2 decade to help characterize permeable path in deep reservoir. The total rea cover 400 km2. With fluid tapped down to 4000m at the max depth with temperature 200-350C. Shallow reservoir: is mainly hosted in carbonates, anhydrites, phyllite and quatzite. It’s characterised by high secondary permeability at its top. Deep reservoir is mainly hosted in metamorphic rocks. Cap rock is as Flysch and Neogene sediments.
  • 600 Km of seismic lines, 20 Km2 of 3D seismic and more than 30 VSPs
  • Seismic horizons they identified here, represent : 1 – fault Horizon 2 part of the shallow reservoir Top of the metamorphic basement is horizon 3. From top of the cap rock to the top of metamorphic basement there is a significant decrease in reflectivity coefficient, downward. This implies that the geological contact within the shallow reservoir is quite well defined. In contrast, within the deep reservoir, the reflection is poorly defined. Horizon 4 is the one that become focus of the study. Its nature is not well ascertained yet. In previous study, the authors deduced that this reflection is linked to geothermal fluid occurrence. Horizon 5 called as horizon K
  • To see how the horizons vertically distributed in projection of 2 directional wells. Note here, secondary fracture and main fracture are indicated mainly in deep reservoir. Horizon K is located down below, not penetrated by the wells.
  • Theoritical : Studies the cause and the effect relationship between interesting petrophysical relationships and seismic response Goal : Determine whether the petrophysical conditions (T,P, injectivity, steam production) are able to produce distinctive anomalies on seismic data Data from 8 wells/boreholes : v,  and relevant petrophysical parameters, then to compute the expected seismic response. Empirical-statistical Verifies investigates the statistical relationships between reservoir data (injectivity, productivity) and reflection signals. The main focus here is their depth occurrence. Techniques : correlation quality between working hypothesis (i.e. fractured level giving distinctive seismic reflection and real data, evaluated by depth deviation classes ( 4 classes : <3% , 3-5% , 5-10%, >10%)
  • Both theoretical and empirical studies indicate that fractured, steam saturated levels give rise to distinctive and potentially diagnostic seismic features. These may occur both in a pre-stack phase, manifest as AVO anomalies, and in a post-stack phase, as high amplitude signals.
  • Both theoretical and empirical studies indicate that fractured, steam saturated levels give rise to distinctive and potentially diagnostic seismic features. These may occur both in a pre-stack phase, manifest as AVO anomalies, and in a post-stack phase, as high amplitude signals.
  • Both theoretical and empirical studies indicate that fractured, steam saturated levels give rise to distinctive and potentially diagnostic seismic features. These may occur both in a pre-stack phase, manifest as AVO anomalies, and in a post-stack phase, as high amplitude signals.
  • Both theoretical and empirical studies indicate that fractured, steam saturated levels give rise to distinctive and potentially diagnostic seismic features. These may occur both in a pre-stack phase, manifest as AVO anomalies, and in a post-stack phase, as high amplitude signals.
  • shallow reservoir : This reservoir is characterised by high secondary permeability at its top.
  • Geothermal is heat from the earth, it is one of the electricity energy source. There are five key elements for geothermal resources, main thing is heat source, mainly as shallow intrusion – Reservoir rocks, it can be hosted in any type rocks, usually associated with volcanic rocks, and frequently with complex geologic setting. This complex geologic setting, in fact may provide fracturing, permeable flow path of the geothermal fluid. So presence of fluid with recharge area is also important, lastly cap rock can be present as a sealing to preserve the convection flow.
  • Seismic refraction surveys have been used to a limited extent because of the amount of effort required to obtain refraction profiles giving information at depths of 5 to 10 km, and the problems caused by the generally high degree of complexity of geological structures in areas likely to host geothermal systems. Seismic reflection – widely applied, with surprisingly valuable results contribution in fracture detection, regional structure, monitoring
  • Transcript of "Seismic method in italy"

    1. 1. Application of Seismic Methods inLarderello – Travale Geothermal Fields Tuscany, Italy Presented by : Yulini Arediningsih April 14, 2009
    2. 2. Outline• Introduction on geothermal systems• Geophysical methods• Seismic Methods• Larderello – Travale geothermal fields• Seismic Data and Methodology• Results• Conclusions• References• Questions ?? 2
    3. 3. IntroductionRECHARGEAREAPERMEABLE FLOWPATH CONVECTION FLOW HEAT SOURCE 3 http://geothermal.marin.org
    4. 4. http://geothermal.marin.org 4
    5. 5. http://geothermal.marin.org 5
    6. 6. Geophysical Methods Include : • Thermal surveys : T gradients, T distribution, heat flow • Resistivity : to delineate field boundaries • Gravity : to define intrusive bodies, heat source • Magnetic survey : boundaries to flows in volcanic areas • Magneto-telluric : fracture detection, monitoring, and regional structure. • Seismic methods : passive and active seismic 6
    7. 7. Seismic Methods Passive Methods : • It can be natural or induced by geothermal activity • Micro Seismic Survey, can be as MEQ survey • Mainly applied for production monitoring Active Seismic • Seismic refraction – only applied in limited extent • Seismic reflection – widely applied, with remarkable results  Challenges : • Very costly • uneasy to manage the data as lower resolution (VP VS change is smaller than in oil), large velocity contrast due to altered rocks 7
    8. 8. Larderello – Travale Geothermal fields • Area of deep field 400km2 • Fluids : tapped within 4000m, 4-7MPa, 200 – 350°C • Shallow reservoir : carbonates, anhydrites, phyllites, quartzites • Deep reservoir : metamorphic series of phyllites, micaschists, gneiss, granites • Cap rock : Flysch and Neogene sediments 8 (From Bertani et al., 2005)
    9. 9. Seismic Data 9 (From Cameli et al, 2000)
    10. 10. Stacked data – seismic line LAR 36 • Decrease in coefficient reflection • Implies well defined geological contact • Overall poorly defined reflections, but sometimes show high energy character • Probably related to geothermal fluid occurrence • The zone has considerable variation in elastic parameters from boreholes logs data 1 – Fault 2 - Flysch/Evaporites formational contact • Hypothesis : the reflections 3 – Top of Metamorphic basement could correspond to certain 4 – Main seismic reflection, deep res.  study focus fractured rocks within the zone 5 – Horizon K • The study : to examine the hypothesis by : Theoretical Study (From Cameli et al, 2000) Empirical Study 10
    11. 11. Migrated data from seismic line LAR 36 with projection of 2 directional wells 1 – Flysch 2 - Tectonic Wedges Complex 3 – Metamorphic basement 4 – Granite 5 – Main seismic reflection, deep res 6 – Horizon K Secondary fracture Main fracture(From Cameli et al, 2000) 11
    12. 12. Methodology Theoretical • Studies the cause and the effect relationship between interesting petrophysical relationships and seismic response • Techniques : wavelet processing, calibrated acoustic impedance sections, AVO analysis • Data from 8 wells/boreholes : velocity, density and relevant petrophysical parameters Empirical-statistical • Investigates the statistical relationships between reservoir data (injectivity, productivity) and reflection signals. • Technique : correlation quality between working hypothesis (i.e. fractured level giving distinctive seismic reflection and real data) evaluated by depth deviation percentage 12
    13. 13. THEORITICAL STUDY • Large velocity and density reduction at fractured production level (3710m)3710 m • High amplitude of the reflection coefficient and synthetic reflection waveforms Suggest presence of steam/gas (within the productive zones) 13 (From Cameli et al, 2000)
    14. 14. THEORITICAL STUDY - AVO RESPONSE• As shear velocity data unavailable, theAVO response computed with “what if ”procedure • Theoretically, with presence of steam/gas (in productive zones)  • Vp/Vs ratio should cause a decrease • Mod. Reflection coeff. increase or remains constant with increase of θ incidence ~ AVO increase too 14 (From Cameli et al, 2000)
    15. 15. Data for empirical study – VSP within the metamorphic basement(From Cameli et al, 2000) 15
    16. 16. EMPIRICAL-STATISTICAL STUDYType of data :► Fracture data (from prod. Wells) • Producing zones PF • Scarcely producing zone SPF • No production TLC► Type of Events Events Detection of Facture Seismic reflection NN None None NF None √ NR √ None► Deviation depth %  < 3% , 3-5 % , 5-10 % , >10% 16 (From Cameli et al, 2000)
    17. 17. Empirical-Statistical study• 73% of seismic reflections correspond to fractured zones, being the depth deviation less than 10%, while the rest (27%) does not correlate or the correlation shows a deviation > 10%.• The VSP data are much more sensitive compared to seismic surface line data.• In contrast, this behavior is less evidenced by the TLC fractures. 17
    18. 18. Conclusions• The empirical study show that, within the Larderello- Travale deep reservoir, 73% of the seismic reflections are related to permeability with a depth deviation of less than 10%.• Both theoretical and empirical studies indicate that fractured, steam saturated levels give rise to distinctive and potentially diagnostic seismic features.• To detect the features noted above, appropriate seismic field acquisition and accurate seismic processing, including wavelet processing and true amplitude and phase control are required. 18
    19. 19. Conclusions• Seismic reflection method has played an important role for identification of deep geothermal targets in Larderrello –Travale fields. It is proven to be the only method providing resolution useful for operative targets deeper than 3 km.• Importantly, it became clear that the seismic method could provide more than the definition of geological structure, namely, information directly related to geothermal production.• A reliable correlation has been verified between deep seismic markers and fractured/permeable horizons in the metamorphic basement. 19
    20. 20. Current status of the Fieldhas been producing since 1960swith 790 MW capacity fromtotal 32 geothermal power plants,providing 4,800 GWh/yr to2 million Italian households,saving 1.1 tonnes of oil equivalent( about 6.8Mbbl of oil equivalent )avoiding 3.8 million tonnes of CO2 emissions 20 (www.europeanenergyforum.eu)
    21. 21. References► Primary sources : o Bertani, R., Bertini, G., Cappetti, G., Fiordelisi, A., Marocco, B.M., 2005, An Update of the Larderello-Travale/Radicondoli Deep Geothermal System, Proceedings World Geothermal Congress 2005, Antalya, Turkey, p. 1-6. o Cameli, G.M., Ceccarelli, A., Dini,I., and Mazzotti, A., 2000, Contribution of the seismic reflection method to the location of deep fractured levels in the geothermal fields of southern Tuscany (Central Italy), Proceedings World Geothermal Congress 2000 Kyushu - Tohoku, Japan, p. 1025 – 1029.► Secondary sources : o Keller, G.V., 1981. Exploration for Geothermal Energy. In: Fitch, A.A. (Ed.), Developments in Geophysical Exploration Methods – 2, Applied Science Publishers., pp. 107-150. o Manzella, A., Gianelli, G., and Puxeddu, M., 1995, Possible models of the deepest part of the Larderello geothermal field, Proceedings World Geothermal Congress 1995, Kyushu - Tohoku, Japan, p.1279 - 1282. o Vanorio, T., De Matteis, R., Zollo, A., Batini,F., Fiordelisi, A., and Ciulli, B., 2004, The deep structure of the Larderello-Travale geothermal field from 3D microearthquake traveltime tomography, Geophysical Research Letters, vol. 31, L07613, doi:10.1029/2004GL019432 21
    22. 22. Thank you andAny Questions ??? 22
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