Sugiura_subbed.qxp 1/4/09 12:41 Page 79
points created by the parallel passive gauge bit. The period of the
highest-frequency response corresponds to the distance between
the bit and the ledge-trimmer sub. The strongest frequency
response appears at the distance between the bit and pads. It
should be noted that the magnitude of all of the oscillation
frequencies is extremely small. The resultant borehole surface is
very smooth, and it exhibits high quality despite the high DLS
yielded by the BHA. Generally, the higher the produced DLS, the
lower the hole quality, with ledges and irregular borehole shapes in
the case of steerable motors.
The spectrum data reveal that adding an undergauge ledge
trimmer to the RSS between the bit and the steering unit creates a
new very-low-magnitude resonant frequency to the borehole
Test results indicate that
this novel mechanical
calliper image helps
engineers troubleshoot
both bit and bottomhole
assembly problems.
calliper spectrum. Also, it suppresses the primary oscillation
frequency response and provides remarkable borehole quality
improvement in problematic drilling conditions and formations.
Conclusion
An RSS with a built-in mechanical calliper has been developed. This
integrated mechanical calliper, while drilling, provides realtime and
memory-based calliper images to aid comparative analyses on
different drill-bit performances and BHA designs.
During the extensive rotary-steerable testing, frequency analysis of
the borehole calliper revealed that there are multiple borehole
oscillation frequencies that correspond to the distance periods
between a bit and other side contact points in the rotary-steerable
BHA. It was discovered that borehole quality can be dramatically
improved by suppressing the peak frequency response of the
borehole calliper.
The use of multidimensional calliper analysis resulted in the
COMPLETE SOLUTIONS
improved bit-gauge and BHA designs for superior balance among
steerability, stability, steering consistency and borehole quality.
OFFSHORE AND ONSHORE
TTS Sense delivers high performance drilling equipment,
Test results indicate that this novel mechanical calliper image helps
multifunctional rigs and world class control systems to
engineers troubleshoot both bit and BHA problems. The effective
the international energy industry. Competence, drive
use of calliper imaging leads to the early detection of borehole
and experience make us a strong partner, providing
oscillation while the BHA is still in-hole and assists in optimising bit
unique solutions and advanced technologies.
and stabiliser selection for subsequent runs. ■
Acknowledgements
I would like to thank PathFinder Energy Services for its willingness
to provide the data obtained with the 12.25-inch hole-size
PathMaker
®
RSS. I am grateful to PathFinder Energy Services for
permitting the publication of this work.
TTS Sense AS
www.tts-sense.com
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