Zonge GDP-32 - Useful TEM Equations

GDP-32
II
INSTRUCTION MANUAL
October 2002 Section 15, Page 12
15.6 USEFUL TEM EQUATIONS
Apparent Resistivity, ρ
a
, (late time)
()
a
I
AA
Vt
TR
E
ρ
=×−
§
©
¨
·
¹
¸
§
©
¨
·
¹
¸
23
5
3
1
63219 3
/
.
(ohm-meters)
Diffusion depth, d:
t
t
d
a
ρ
σ
4040 == (meters)
Equivalent depth of investigation, D:
t
t
D
a
ρ
σ
2828 == ( m e t e r s )
where:
A
T
= transmitter moment in square meters
A
R
= Receiver moment in square meters
I = Transmitter current in ampere t = Time in milliseconds
V = Received voltage in microvolts σ = Conductivity in siemens/meter = 1/ρ
Depth of investigation plot for TEM assuming a noise level of 1 nanovolt per square meter,
showing the absolute limits for 100 by 100 and 500 by 500 m loops.
1
0
0
m
x
1
0
0
m
l
o
o
p
,
1
0
a
m
p
s
5
0
0
m
x
5
0
0
m
l
o
o
p
,
2
0
a
m
p
s