Calibration of a neutron log in partially saturated media IV: Effects of sonde-wall gap

Conference · Sun Jan 01 04:00:00 EST 1984

OSTI ID:6622820

Axelrod, M C; Hearst, J R

A gap between a neutron sonde and the wall of a borehole can have a significant effect on the observed count rate. The authors have experimentally determined this effect to be linear with gaps as large as 2.5 cm. The count rate is given by N/sub N/ = K/sub 0/ + K/sub 1/g where K/sub 0/ is the count rate that would be observed at zero gap, and g is the gap. The parameters K/sub 0/ and K/sub 1/ are dependent on both water (ie. hydrogen) content and bulk density. In many situations failure to correct the count rate for this gap effect can result in a significant degradation in the accuracy of the water content calculated from the count rate. In a dry borehole, K/sub 1/ is small at zero formation water content, and increases with formation water content. In a water-filled borehole, K/sub 1/ is large at zero formation water content, and tends to decrease with increasing formation water content, becoming zero, as of course it must, if the formation is pure water.

• Research Organization: Lawrence Livermore National Lab.
• OSTI ID: 6622820
• Report Number(s): CONF-8406110-
• Country of Publication: United States
• Language: English

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03 NATURAL GAS
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47 OTHER INSTRUMENTATION
CALCULATION METHODS
CALIBRATION
CAVITIES
DENSITY
EQUIPMENT
EXPLORATION
EXPLORATORY WELLS
GEOLOGIC DEPOSITS
GEOPHYSICS
GROUND WATER
HYDROGEN COMPOUNDS
INTERSTITIAL WATER
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NEUTRON LOGGING
OXYGEN COMPOUNDS
PETROLEUM DEPOSITS
PHYSICAL PROPERTIES
POSITIONING
PROBES
RADIOACTIVITY LOGGING
RESERVOIR ROCK
RESOURCES
SATURATION
WATER
WATER SATURATION
WELL LOGGING
WELL LOGGING EQUIPMENT
WELLS