Sugiura_subbed.qxp 27/3/09 04:24 Page 77
While-drilling Calliper Images Enhance Rotary-steerable Performance
Figure 1: 12.25-inch Hole-size Push-the-bit Rotary-steerable System
shown in Figure 1, was designed exclusively for this systematic testing. Figure 2: The Short Parallel Passive Gauge Bit (MDi616)
The main objective of the controlled tests was to establish the
maximum dogleg using various bit gauge configurations and at the
same time to evaluate the system for stability, steerability, dynamic
light scattering (DLS) consistency and borehole quality. For all tests,
similar surface parameters were used: weight on bit (WOB) 10–20klbs,
rotary speed 110–120rpm, flow rate 600gpm. The RSS was set for
91% offset setting. Realtime and memory-based vibration data and
calliper images were used to evaluate bit/BHA performance. This
analysis was used to understand whether the geometry and drill-bit
changes influenced RSS performance and resultant borehole quality.
Realtime and memory-based vibration data and calliper images were
used to evaluate bit/BHA performance. The tapered-gauge bit with a ledge trimmer created the highest borehole
quality, stability and toolface controllability. There were no signs of
Test Results borehole ledging or spiralling in the 2D and 3D calliper images in both
In this set of experiments, various PDC bit gauge profiles were tested sandstone and limestone. Due to the added length with the ledge-
to evaluate hole quality and hence the knock-on effect of improved trimmer sub (about 1ft), the maximum build rate was approximately
steerability and stability in a hard carbonate rock application 3.9°/100ft in limestone. In all of the tests conducted, the better-quality
(limestone). Four different PDC bits and one tricone (insert) bit were borehole was always obtained with the use of a ledge trimmer.
tested. The PDC bits tested were tapered gauge, tapered gauge with a
ledge-trimmer sub, short parallel passive gauge and long passive gauge Among the different PDC bits without a ledge trimmer, the short
with undercut. parallel passive gauge bit shown in Figure 2 produced the highest build
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