technical specs
HSHA RATE GYRO
- HOW IT WORKS
Outline
The HSHA
Rate Gyro is the second generation multishot
borehole survey tool from Applied Technologies
and has two distinct operating modes.
For dip angles ranging from -90° to -75°
the tool operates in Gyro Compass Mode and
for dip angles ranging from -75° to +15°
it is run in continuous high-speed mode.
The gyro used is a single axis rate integrated
fully floated in oil gyro which rotates
at 48,000RPM. There are two linear accelerometers
utilized in addition to an angular accelerometer.
Both the gyro and the accelerometers are
mounted on gimbals that may be rotated internally
about the tool axis.
Gyro Compass Mode. (Dip range -90° to -75°)
In this mode the gimbal is rotated in four
discreet 90-degree increments about the
tool axis. The Earth Rate vector and gravity
vector are measured at each position. From
this the inclination angle and azimuth angle
from true north of the tool can be determined.
Each Gyro compass reading is completely
independent from the previous readings.
The gyro compass technique reduces major
accelerometer and gyroscopic sensor bias
errors. Gyro compass readings are used as
an independent check at the collar and end
of hole when operating in high-speed mode.
High Speed Mode. (Dip range -75° to +15°)
In continuous survey mode, or as it is more
commonly know, high-speed mode, the tool
operates as an attitude referencing system.
The gimbal is roll stabilized such that
the input axis of the gyro and the canted
accelerometer are held in the vertical plane.
The tool then measures all the azimuth variations
from the initialisation point continuously
while traversing downhole. The azimuth at
the initialisation depth is accurately determined
by taking and averaging a minimum of 6 gyrocompass
readings to achieve a standard deviation
better than 0.2° prior to roll stabilizing
the gimbal.
Inclination is measured directly from the
canted accelerometer. The input axis of
this accelerometer is aligned with that
of the gyro and is canted at approximately
18° from the tool axis. This allows the
tool to survey through horizontal to approx
+15° dip.
For technical specs on this tool click HERE.
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Target DHS Gyro
