Geology Reference
In-Depth Information
velocity measured by seismic waves that have wavelengths 1,000 times as long.
The analyst measures the transit time in microseconds per foot to
determine rock type and porosity.
Temperature Logs
The temperature log is useful for measuring temperature gradients,
lithology changes, and water flow in the vertical direction. The logging can be
done either from top down or from bottom up, and it is common to log in both
directions. However, for the greatest precision, logging from the top down is
preferred because the water has not been disturbed by the passing of the tool.
Caliper Logs
The caliper log is used to measure borehole diameter as a function of
depth. It shows the boundaries between soft shales and hard limestones very
clearly and with better depth, precision than other logging tools. It is useful to
find evaporites and washouts of shale.
Casing Collar Logs
The casing collar log is used to count joints of casing to know exactly how
far down the hole specific geologic layers are. The casing collar log is used in
conjunction with the natural gamma log to provide locations for casing
perforations or for hydrologic measurements such as packer tests and drill stem
tests. (Packers are plugs used to isolate fluid under pressure in a specific
segment of pipe in a hole.)
Dip-Meter Logs
The dip-meter log is obtained from three resistivity tools placed at
different azimuths around the sonde. This log of measures local dip of geologic
layers within a borehole.
Search WWH ::
Custom Search