39
Fig. 2.8 Porosity logs determined by resistivity measurements on three gravity cores from the South Atlantic (see
also Fig. 2.7 and Table 2.1). Gray curve: Boyce’s (1968) values were used for the constants (a) and (m). Black curve:
(a) and (m) were derived from the slope and intercept of a linear least square fit. These values are given at the top
of each log. Superimposed are porosities determined on discrete samples by weight and volume measurements
(unpublished data from P. Müller, University Bremen, Germany).
the porosity log which agree well with the gamma
ray attenuation densities ((c), gray curve) and
show less scatter.
Though resistivities are only measured halfautomatically including a manual insertion and
removal of the probe, increments of 1 - 2 cm can
be realized within an acceptable time so that more
fine-scale structures can be resolved than by
analysis of discrete samples. However, the real
advantage compared to an automated gamma ray
attenuation logging is that the resistivity measurement system can easily be transported, e.g.
onboard of research vessels or to core repositories, while the transport of radioactive sources
requires special safety precautions.
2.2.4
Electrical Resistivity
(Inductive Method)
A second, non-destructive technique to determine
porosities by resistivity measurements uses a coil
as sensor. A current flowing through the coil
induces an electric field in the unsplit sediment
core while it is automatically transported through
2.2
Porositiy and Wet Bulk Density
Fig. 2.8 Porosity logs determined by resistivity measurements on three gravity cores from the South Atlantic (see
also Fig. 2.7 and Table 2.1). Gray curve: Boyce’s (1968) values were used for the constants (a) and (m). Black curve:
(a) and (m) were derived from the slope and intercept of a linear least square fit. These values are given at the top
of each log. Superimposed are porosities determined on discrete samples by weight and volume measurements
(unpublished data from P. Müller, University Bremen, Germany).
the porosity log which agree well with the gamma
ray attenuation densities ((c), gray curve) and
show less scatter.
Though resistivities are only measured halfautomatically including a manual insertion and
removal of the probe, increments of 1 - 2 cm can
be realized within an acceptable time so that more
fine-scale structures can be resolved than by
analysis of discrete samples. However, the real
advantage compared to an automated gamma ray
attenuation logging is that the resistivity measurement system can easily be transported, e.g.
onboard of research vessels or to core repositories, while the transport of radioactive sources
requires special safety precautions.
2.2.4
Electrical Resistivity
(Inductive Method)
A second, non-destructive technique to determine
porosities by resistivity measurements uses a coil
as sensor. A current flowing through the coil
induces an electric field in the unsplit sediment
core while it is automatically transported through
2.2
Porositiy and Wet Bulk Density