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Acoustic velocity properties of Danian limestone section
exposed at the Curfs quarry, Southeastern Netherlands
Ohwoghere Asuma, Oghenero
Department of
Geology, Delta State University Abraka, Delta State,
Nigeria. E-mail:
ohwonero@hotmail.com.
Accepted 15 March, 2012 |
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In order to establish the relationship existing between the
seismic velocity and petrophysical properties of limestone,
ultrasonic pulse transmission technique under simulated
pressure of 2.5 to 10 Mpa and at a frequency of 300 to 800
kHz was used in the determination of both compressional-wave
and shear- wave velocities. The measurements were carried
out for both dry and fluid saturated limestone obtained from
the Curfs quarry in Limburg, Southeastern Netherlands.
Compressional wave velocities values range from 2218.2 to
3280 ms-1 for dry samples and 2448 to 3730 ms-1
for fluid saturated samples. While those for shear-wave
velocities values range from 2024 to 2982 ms-1
for dry samples and 1568.2 to 2024 for fluid saturated
samples.These velocities values were used to constrained
limestone into two lithogic units- the compacted limestone
units, also know as the hardgrounds (high velocity values)
and undercompacted limestone units (low velocity values).
The compressional wave velocities of fluid saturated
limestone samples are relatively higher than those obtained
for equivalent dry ones, while the shear wave velocities of
the same fluid saturated limestone samples were lower than
the dry ones. The degree of diagnesis in the weakly cement
limestone is responsible for the high value of both
compressional- wave and shear wave velocities obtained from
the acoustic velocity measurement. The velocity obtained
from the time average equation is much more than the
velocity obtained from the laboratory measurement of
velocity for the curfs quarry.
Key
words:
Acoustic, compressional and shear-wave
velocity, cement, fluid saturation. |
