KIRTLAND AIR FORCE BASE ALBUQUERQUE, NEW MEXICO ...

APPENDIX B
Redox potential or the oxidation/reduction of sulfide mineralization such as pyrite, and
Electromechanical potential or streaming potential from fluid flow directly into or out of the
formation.
The 16-inch Short Normal Resistivity and 64-Inch Long Normal Resistivity logs measure apparent
formation resistivity, utilizing both current and potential electrodes in the borehole and a reference
surface electrode. The formation resistivity, measured in ohm-meters, is affected by grain size, porosity,
and pore fluid. The 16- and 64-inch normal is a quantitative measurement. The radius of investigation of
this tool is related to the spacing between the current and potential electrodes, which in this case is 16 or
64 inches. In highly resistive formations, the radius of investigation is reduced. In hard, low porosity
crystalline formations with very fresh pore water, the apparent resistivity is high. Fracturing in a
crystalline environment has the effect of increasing apparent porosity and thus reducing apparent
resistivity.
The Guard Resistivity measurement is a focused resistivity log. It consists of two guarding electrodes
and a current electrode. In the fluid-filled portion of the borehole, the log is used for very thin bed
resolution and to approximate formation resistivity.
The Induced Polarization (IP) log is a time domain measurement of the residual charge storage (or decay
or secondary voltage) after the formation has been excited with a constant current pulse that is then
turned off. Measurement of the secondary voltage corresponds to the polarizability of the formation.
The secondary voltage is normalized with respect to the primary voltage pulse with IP effect expressed as
the ratio of secondary voltage to primary voltage. Log values are displayed as a ―percentage‖ with 1
percent IP response corresponding to 10 mV/v.
IP logs are generally used qualitatively to semi-qualitatively to detect disseminated sulfide (pyrite) and
sometimes montmorillonite clay.
Caliper Measurement
The caliper log is a mechanical three-arm or a single-arm measurement that physically determines the
average diameter of a borehole. The diameter increases in cavities and, depending on the drilling
techniques used, in weathered zones. An apparent decrease in borehole diameter may result from mud or
drill cutting accumulation along the sides of the borehole and in the bottom of a boring. Data from the
caliper log is used to vertically locate cavities or washouts and to diameter that directly affects the
response of other measurements.
Sonic Measurement A sonic log shows travel times of acoustic waves through rock in microseconds. It
is sometimes accompanied by an amplitude log and a Variable Density Log (VDL) of the full sonic
waveforms. Spacings from 18 to 60 inches or more can be made depending on the specific objectives.
Sonic logs can only be obtained in a fluid filled borehole. Additionally, high-quality sonic logs may not
be acquired where the formation is not fully saturated or poorly consolidated even if the borehole is fluid
filled in this region.
The transmitter on the sonic probe emits an approximate 30 Khz ultrasonic pulse twice a second. This
waveform passes through the borehole fluid in all directions at the fluid velocity (approximately 5000 ft
per second). When it reaches the borehole wall, the waveform travels through the rock mass at higher
velocities and is refracted to 2 different receivers on the logging probe 1 ft apart.
Kirtland AFB
SOPs for Field Investigations B-30 April 2004