Geothermal Resource Exploration


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Geothermal Resource Exploration

  1. 1. Geothermal resource  exploration using MT  in the  west Anatolian extensional  province Mehran Gharibi Ersan Turkoglu Quantec Geoscience
  2. 2. Outline • Introduction to Quantec Technology & MT • Geothermal exploration using MT • • • Geothermal potential of western Turkey 3D MT Inversion and Interpretation Summary
  3. 3. Quantec Geoscience Limited is a world leader in non-seismic ground geophysical exploration with worldwide offices since 1986. Quantec offers state-of-the-art Deep Earth Imaging Technologies thru our proprietary Orion 3D, Titan 24 DCIP&MT and Spartan MT data acquisition, processing and interpretation, as well as the full suite of conventional EM survey methods. Toronto, Canada Reno, USA Hermosillo, Mexico QIPS, Barbados Arequipa, Peru Santiago, Chile Lobatse, Botswana Mendoza, Argentina Brisbane, Australia
  4. 4. TECHNOLOGY Stand alone  5‐channel MT 2D DCIP & MT 3D DCIP & MT
  5. 5. Electric Field Sensors
  6. 6. Magnetic Field Sensors Coil Calibration Chamber • Quantec owns and employs a calibration room for calibrating magnetic field sensors. • The room provides both 3-layer passive shielding and active field cancellation. • Each individual magnetic coil is calibrated before deployment to the field and coil calibration constants are archived for each and every job. • Only two facilities of its kind in the world.
  7. 7. Introduction  To Magnetotelluric (MT) Method
  8. 8. MT Signal Sources Lower Frequencies: f < 1 Hz Interaction  of the solar wind with the earth’s  magnetic field NASA E(ω ) = Z(ω )B(ω ) Higher Frequencies: f > 1 Hz  Global lightning activities Thunderstorms
  9. 9. NASA
  10. 10. Seasonal Lightning Map National Space Science and Technology Centre
  11. 11. MT Signal Sources • Sunspot activity has 11 year period. • Last solar maximum was in 2001. • Past few years were tough for MT acquisition especially at high noise areas.
  12. 12. Penetration Depth (Skin Depth) δ = 503 ρT δ = 503 100Ωm × 4s δ = 10060 m ~ 10 km ~ 100Ωm f = 10 Hz ⇒ δ = 1.6km f = 40 Hz ⇒ δ = 0.8km ~4s Increasing depth
  13. 13. Magnetotellurics (MT) 100 ohm.m 10 km 10 ohm.m 1000 ohm.m E(ω ) = Z(ω )B(ω ) ρa = 1 μ 0ω Z Ex RhoXY ≈ Hy 2 NASA φ = arg(Z ) Ey RhoYX ≈ Hx
  14. 14. Interpretation of the MT Data:  • Data ⎛ 0 ⎜ ⎜− Z ⎝ Z⎞ ⎟ 0⎟ ⎠ ⎛ 0 ⎜ ⎜Z ⎝ yx Z xy ⎞ ⎟ 0 ⎟ ⎠ ρ • Inversion • Resistivity Model 2‐D Z xy ⎞ ⎟ Z yy ⎟ ⎠ ρxy, ρyx 1‐D ⎛ Z xx ⎜ ⎜Z ⎝ yx 3‐D
  15. 15. What is geothermal? Why Turkey? Why MT?
  16. 16. What is geothermal? 2 • Heat energy of the earth is  called geothermal energy. • Geothermal energy exposed  to the surface as a result of  Earth’s cooling mechanism,  convection. 3 1 First geothermal  power plant in  Larderello in 1904  by Prince Piero Ginori Conti. • 90 countries have  geothermal potential and 70  of those already utilized  geothermal energy. • USA, Philipines, Iceland,  Indonesia and Italy are some  of the largest geothermal  user countries.
  17. 17. What is geothermal? 2 3 1 Courtesy of Promete Jeotermal Courtesy of Promete Jeotermal
  18. 18. Regional Tectonics • Northward motion of African and Arabian plates • Closure of the Tehys Ocean 13 Ma • Arabia‐Eurasia collision and uplifting  Courtesy of Promete Jeotermal • Development of NAF and EAF • Extrusion of Anatolian Block • Trench roll back and extension.
  19. 19. Geothermal Potential of Turkey Curie point (580 C) depth  and heat flow maps of  Turkey (Aydin, et al., 2005). Note that the Curie depth  in western Anatolia is ~10  km. This is significantly  shallower than the rest of  the country. Higher heat flow values  >100 mW/m2 are also  coincident with shallow  Curie depth.
  20. 20. Geothermal Potential of Turkey The geothermal systems  associated with volcanism are  common in the central and  eastern part. 500 m depth temperature distribution map, (Korkmaz et al., 2010) Many hot springs and wells  with  temperatures >200°C are  indicating the geothermal  potential in western Turkey.  Faults play an important role  as well as the reservoir in  western Turkey. Delineating of the basement  structure and the faults is  direct interest to geothermal  exploration in western Turkey Location of major geothermal fields in Turkey (Serpen et al., 2009)
  21. 21. Why MT for Geothermal? High resistivity contrast Deep penetration Portable Non‐invasive “Lower” cost after Cumming et al. 2009 after Cumming et al. 2009 Kuyumcu et al., 2009
  22. 22. Denizli MT Survey • 92 MT sites were collected in April, 2012. Survey  area is highly industrialized mainly within the  graben. • Remote site was located 60 km away from the grid. • 48kHz, 12kHz and 1kHz (continuous) sampling  rates were used for data acquisition. Courtesy of Promete Jeotermal
  23. 23. Denizli MT Data • High quality 5‐channel MT data were acquired by using Spartan MT data loggers. Courtesy of Promete Jeotermal
  24. 24. Denizli MT Data • High quality 5‐channel MT data were acquired by using Spartan MT data loggers. Courtesy of Promete Jeotermal
  25. 25. Denizli MT Data • High quality 5‐channel MT data were acquired by using Spartan MT data loggers. Courtesy of Promete Jeotermal
  26. 26. Denizli MT Data • High quality 5‐channel MT data were acquired by using Spartan MT data loggers. Courtesy of Promete Jeotermal
  27. 27. Denizli 3D MT Inversion • • • • • • • • • • • Air cells Average site spacing is 1‐2 km 87 sites used for 3D inversion Full MT tensor (Zxx, Zxy, Zyx, Zyy) 8% error floor Topography was included 30 Ohm‐m half‐space initial model Dx, Dy, Dz: 400m, 400m, 40m 1000 Hz to 0.002 Hz frequency band Total of 18 frequency Final RMS was 1.25  WSINV3DMT (Siripunvaraporn etal., 2005)  Air cells Initial model resistivity: 30 Ohm‐m Courtesy of Promete Jeotermal 220km
  28. 28. Denizli 3D MT Model Expected cross‐section (2 km) of the Denizli Graben (Akman, 2012) Denizli graben contains two types of infills. 1. Ancient: 660 m thick Middle Miocene‐Middle Pliocene deposits controlled and deformed  by ~N‐S extension then compression in the latest Pliocene (Kocyigit, 2005). 2. Modern: 350 m thick, undeformed Plio‐Quaternary deposits (Kocyigit, 2005).
  29. 29. Denizli 3D MT Model High Res. Low Res. Courtesy of Promete Jeotermal Courtesy of Promete Jeotermal
  30. 30. Resistivity Cross‐sections South Jeotermal Courtesy of Promete North Courtesy of Promete Jeotermal
  31. 31. Resistivity Cross‐sections South North Courtesy of Promete Jeotermal Courtesy of Promete Jeotermal
  32. 32. Resistivity elevation maps ‐500 m ‐1000 m Courtesy of Promete Jeotermal
  33. 33. Resistivity elevation maps ‐1500 m ‐3000 m Courtesy of Promete Jeotermal
  34. 34. Conclusions: – Closely spaced MT sites required to build better constrained models as well as static shift control. – Good quality MT data can be collected even around industrialized and populated areas. – MT imaged the sedimentary fill of the Denizli graben and underlying Menderes metamorphics. – Well locations were determined by use of MT, seismic and structural geology to reduce drilling risk. – Computational requirements for 3D inversion has been matched by recent developments on computer clusters. However, most MT surveys are designed as a grid and more MT stations are collected than ever before.
  35. 35. Pamukkale, Denizli, Turkey Thank You