Specifications

University of Pretoria etd – Combrinck, M (2006)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 100 200 300 400 500
Depth [m]
Imaged Conductivity [S/m]
0
0.01
0.02
0.03
0.04
0.05
0.06
Imaged Conductivity [S/m] (20m)
2m
5m
10m
15m
20m
Figure 4-39: Imaged conductivity for a 2 S/m layer of varying thickness at 150m depth in a 0.02
S/m half space – linear scale.
Except for the 2 m layer, all the curves exhibit the high contrast behaviour. The thicker
the layer becomes, the closer the curves resemble the two layer case with very little or no
influence from the earth below the conductive layer contributing to the signal.
The effect of varying depth of a conductive layer is shown in Figures 4-40 – 4-42. The
width of the anomaly increases with depth to top of the conductive layer while the
amplitude decreases. One case of special interest is the layer at 50m depth. For the host
rock conductivity of 0.02 S/m and the chosen system parameters, the shallowest depth of
investigation is in the order of 100 m. However, if there is a conductive layer shallower
than this, the depth of investigation is adapted to that. The curve is distorted compared to
those of the deeper layers in the sense that there is no rise from the host rock response into
the conductive layer. It actually takes a shape more indicative of a two layered earth.
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