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WIRELINE LOGGING
Wireline Logging is a continuous record of
measurements made in a borehole by a probe
able to respond to some variations in some
physical property of the rocks through which the
borehole is drilled.
Probes are lowered into boreholes and
depending on the type of probe, take
different measurements of the rock and
transmit the information to a computer
via a signal decoding unit.
Prior calibration of the probe (against
known value materials) allows us to
process the information into engineering
units (ie. grams/cc or mm etc.)
Data is displayed on paper plots and
digital formats. Log ascii standard (LAS),
log industry standard (LIS) and portable
document format (pdf) are common
methods of presenting data.
In coal logging as well as non coal
applications, the ability to log with
geophysical probes to produce a
continuous and objective record of subsurface
formations is a great asset. It
removes many of the uncertainties
associated with the interpretation of
chipping records and incomplete core.
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COAL LOGGING
- Natural Gamma
Calibrated value in API units
- LSD
Long spaced density in gmcc
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SSD
Short spaced density in gmcc.
The dual spacing of this density is used for the determination of accurate calibrated bulk density, seam thickness and quality of the seam. The variable sampling rate gives excellent control over vertical resolution and the tungsten collimation allows measurements in air filled holes up to 300mm in diameter
- Caliper
Is used to determine the borehole diameter and is also used for the real time borehole volume curve in cubic meters. It also indicates caving zones as well as possible fractures.
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