This document summarizes a magnetotelluric (MT) survey conducted in Denizli, Turkey to explore the geothermal potential of the region. The survey involved collecting high quality MT data from 92 sites using Spartan MT data loggers. The data was inverted in 3D using WSINV3DMT, producing resistivity models of the subsurface down to 3000 meters depth. The models image the sedimentary fill of the Denizli graben and the underlying bedrock, helping to identify potential geothermal reservoirs and determine well locations to reduce drilling risks. The MT survey was able to map subsurface resistivity variations despite the industrialized nature of the area, demonstrating the effectiveness of MT for geothermal exploration.

1. Geothermal resource
exploration using MT
in the
west Anatolian extensional
province
Mehran Gharibi
Ersan Turkoglu
Quantec Geoscience

2. Outline
•
Introduction to Quantec Technology & MT
•
Geothermal exploration using MT
•
•
•
Geothermal potential of western Turkey
3D MT Inversion and Interpretation
Summary

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
www.quantecgeoscience.com

4. TECHNOLOGY
Stand alone
5‐channel MT
2D DCIP & MT
3D DCIP & MT

6. Electric Field Sensors

7. 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.

8. Introduction
To
Magnetotelluric (MT) Method

9. 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

10. NASA

11. Seasonal Lightning Map
National Space Science and Technology Centre

12. 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.

13. 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

14. 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

15. 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

16. What is geothermal?
Why Turkey?
Why MT?

17. 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.

18. What is geothermal?
2
3
1
Courtesy of Promete Jeotermal
Courtesy of Promete Jeotermal

19. 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.

20. 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.

21. 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)

22. 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

23. 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

24. Denizli MT Data
• High quality 5‐channel MT data were acquired by using Spartan MT data loggers.
Courtesy of Promete Jeotermal

25. Denizli MT Data
• High quality 5‐channel MT data were acquired by using Spartan MT data loggers.
Courtesy of Promete Jeotermal

26. Denizli MT Data
• High quality 5‐channel MT data were acquired by using Spartan MT data loggers.
Courtesy of Promete Jeotermal

27. Denizli MT Data
• High quality 5‐channel MT data were acquired by using Spartan MT data loggers.
Courtesy of Promete Jeotermal

28. 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

29. 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).

30. Denizli 3D MT Model
High Res.
Low Res.
Courtesy of Promete Jeotermal
Courtesy of Promete Jeotermal

31. Resistivity Cross‐sections
South Jeotermal
Courtesy of Promete
North
Courtesy of Promete Jeotermal

32. Resistivity Cross‐sections
South
North
Courtesy of Promete Jeotermal
Courtesy of Promete Jeotermal

33. Resistivity elevation maps
‐500 m
‐1000 m
Courtesy of Promete Jeotermal

34. Resistivity elevation maps
‐1500 m
‐3000 m
Courtesy of Promete Jeotermal

35. 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.

36. Pamukkale, Denizli, Turkey
Thank You