Geothermal handbook: PlanninG and Financing power Generation t e c h n I c a L r e p o r t 2 / 2

Geophysical exploration i
Several methods can be used to measure the conductivity or
resistivity of subsurface rocks; the Transient Electro Magnetic (TEM) method and the Magneto
Telluric (MT) method are most commonly used today. These two methods complement each
other since the MT shows results at great depth while the TEM shows results at shallow depth
and resolves the telluric shift problem of the MT. 
• 
Geophysical exploration with bouguer gravity
measurements complement
MT and TEM
measurements by measuring anomalies in the density distribution of subsurface rocks,
thereby permitting the identification of large geological structures with boundaries
related to tectonic features that in turn may lead to faults and fractures. Results of
geophysical exploration, used in combination with geological data, can lead to the
location of the heat source and provide targets for the test drillings (exploration drillings).
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In this context, the term “exploration phase” refers to the second phase in the detailed breakdown of the project cycle. This usage is distinct 
from “exploration” in a broad sense, which consists of the first three phases, including the test drilling phase. The latter usage is more common 
for the oil and gas industry. 

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G e o t h e r m a l H a n d b o o k : P l a n n i n g a n d F i n a n c i n g P o w e r G e n e r a t i o n 
•