Description
Applications
Schematic illustration of the Resistivity-at-the-Bit tool
(LWD-RAB).
Specifications
ODP Logging Services, Lamont-Doherty Earth Observatory, Rt. 9W,
Palisades, NY 10964
Logging-While-DrillingResistivity-at-the-Bit Tool
♦ Detection of resistivity heterogeneity viaazimuthal
resistivity images
♦ Lithology estimation♦ Instantaneous detection of casing and
coring
points♦ Accurate resistivity when mud is salty or
formation resistivity is high♦ Detection of early invasion of
borehole fluids
into the formation
The Resistivity-at-the-Bit tool (LWD-RAB) makesazimuthal
resistivity and gamma ray measurements whiledrilling. Using an
azimuthal positioning system,measurements are acquired around the
borehole to create ahigh resolution, 360-degree resistivity image
of the drilledhole. The RAB tool may be connected directly behind
thebit or further back in the bottom hole assembly. It may berun
with other LWD tools such as the ADN, ISONIC orNMR. Typically, the
RAB data are stored in memory withinthe tool and retrieved at the
end of the bit run. As an option,the data may be transmitted to a
surface acquisition systemif a Measurement-While-Drilling (MWD)
power pulse toolis run in conjunction with the RAB.
Assembly of the RAB tool aboardthe JOIDES Resolution.
Optional uphole connector
Batteries
Upper sensor
Middle sensor, containing focused ring electrode
Azimuthal gamma ray
Field-replaceable stabilizer
Lower sensor
Float valve boreRbit electrode
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