Geothermal Method in Geophysics

1. Geothermal
By
Zaidoon T. Abdulrazzaq

2. Introduction
The sun is the main source of heat we feel on the earth, but a little part of the rays can
penetrate deep into the earth and does not exceed a few hundred meters. So little impact on the
Earth's interior components can be omitted as compared with the heat inside the earth.
Currently believed to be the primary source of thermal energy in the earth is the process of
radioactive decay of long-lived isotopes, and other sources such as the preliminary heat and the
heat liberated by accumulation as a result of the gravitational influence.
Heat travels gradually or sudden from the ground to the roof. Examples include (volcanoes
and hot springs). Leaking heat working through layers of earth to stimulate the occurrence of
different geological processes (such as tectonic movements, fires activities).
The study of the thermal behavior of the earth of the branches of geophysics task because
of its association with all hypotheses concerning the origin and evolution of the earth.

3. Hot Springs
Hot springs in Steamboat Springs area.
http://www.eia.doe.gov/cneaf/solar.renewables/page/geothermal/geothermal.html

4. Geysers
http://en.wikipedia.org/wiki/Geyser
Clepsydra Geyser in Yellowstone

5. Geothermal reservoirs

6. Theories and hypotheses heat flow from the Earth
The most important of these theories are (Convection) inside the
Mantel by assumptions associated with the continental's drift,, the spread
of the seafloor and plate tectonics.

7. Thermal properties of rocks
 Temperature increases with increasing depth. As a result, the
heat flowing to the top of the ground, and that the amount of flow
q depends on two important two characteristics:
 The thermal conductivity of the rocks
 Thermal gradient
And in relation
q = -K grad T
Whereas:
- Grad T is (ᵹT/ᵹZ) temperature increase with depth rate. q is
measured in units of energy per unit area (W / m).

8. Earth Temperature Gradient
http://www.geothermal.ch/eng/vision.html

9. Terrestrial heat flow
The heat transmitted from the ground to the roof and then
spread in the air called (Terrestrial heat flow), which accounts
for inspecting the earth of thermal energy. The current rate of
loss of heat from the Earth's surface is estimated at (4 * 1013)
Watts. The energy lost as a result of earthquakes and volcanic
activity are less so.
Estimate the heat Flow requires two measurements:
- Thermal gradient Measurements (ᵹT/ᵹZ)
- Thermal conductivity of rocks K.
Then the heat flow per unit area through the expense of the relationship
q = K ᵹT/ᵹZ
Heat Flow Measurements:

10. The relationship between heat flow and the age
of the rocks
There is a strong relationship with the heat flow with the age of
the crust. In the ocean, this relationship represents the age of the
Crust Mafic age. Either continents identifies old relationship the
last Tectonothermal event.
The common belief is that the radioactivity, and the energy
produced by the gravity are two main sources of geothermal and be the
heat generated by radiation often decay of isotopes (uranium, thorium
and potassium), the table shows the abundance of these isotopes in the
main types of rocks consisting of the crust and the mantel. Either
sources of heat inside the mantel, they are:
- The heat coming from the Earth's core to mantel.
- The heat generated by radioactive decay inside the rocks of mantel.
The generation and transmission of heat into the earth

12. Heat sources:
Earth’s internal heat
(Heat loss)
Radioactive decay
(Heat gain)

14. Temperatures inside the Earth
The simplest way to measure temperature is drilling a hole and use a
sensitive thermometer. Or the use of alternative methods such as (mines
wells, tunnels, oil wells). These methods show an increase of temperature at
any position with the depth and rate of an increase of about 3° per 100 meters
depth in non-volcanic areas.
To calculate the temperature of the deep areas must use indirect methods
such as seismic velocities and changes in the electrical conductivity.
Thermal prospecting methods
In the fields of research and detection of thermal sources under the surface we
have to determine the cause of positional changes in temperature below the surface,
namely:
1. Groundwater effectiveness
2. Chemical activity resulting from the exothermic reactions
3. The existence of localized sources of heat radiation
4. The difference in conductivity of the rocks
5. The presence of volcanic and hydrothermal sources

15. Exploration for geothermal sources
Due to the increasing importance of geothermal resources as
sources of alternative energy because of the growing demand.
There are several ways to explore them
1. Thermal methods, which include
- Heat Check-in wells
- Survey the flow on the surface
2. Electrical and electromagnetic methods
Geothermal exploration depends on the ability the electrical conductivity
of rocks, which increases with increasing temperature (especially increased
water temperatures give high conductivity and low resistivity), while the steam
gives a few high conductivity and resistivity.
3. Seismic methods, both active and passive.
4. Gravity surveys.

16. Advantages
 Available all the year around.
 Independent of weather
 Clean Resource – Very little emissions or overall
environmental impact.
 Economically

17. Disadvantages
 Not widespread source of energy
 High installation costs
 Can run out of steam
 May release harmful gases
 Transportation
 Earthquakes

18. Geothermal in Context
Energy Source 2000 2001 2002 2003 2004P
Total a 98.961 96.464 97.952 98.714 100.278
Fossil Fuels 84.965 83.176 84.070 84.889 86.186
Coal 22.580 21.952 21.980 22.713 22.918
Coal Coke Net Imports 0.065 0.029 0.061 0.051 0.138
Natural Gasb 23.916 22.861 23.628 23.069 23.000
Petroleumc 38.404 38.333 38.401 39.047 40.130
Electricity Net Imports 0.115 0.075 0.078 0.022 0.039
Nuclear Electric Power 7.862 8.033 8.143 7.959 8.232
Renewable Energy 6.158 5.328 5.835 6.082 6.117
Conventional Hydroelectric 2.811 2.242 2.689 2.825 2.725
Geothermal Energy 0.317 0.311 0.328 0.339 0.340
Biomassd 2.907 2.640 2.648 2.740 2.845
Solar Energy 0.066 0.065 0.064 0.064 0.063
Wind Energy 0.057 0.070 0.105 0.115 0.143
http://www.eia.doe.gov/cneaf/solar.renewables/page/geothermal/geothermal.html
U.S. Energy Consumption by Energy Source, 2000-2004 (Quadrillion Btu)

19. Global Geothermal Sites
http://www.deutsches-museum.de/ausstell/dauer/umwelt/img/geothe.jpg

20. Thanks For Your
Attention !
Any Questions ?