January 2016
Oilfield Technology
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29
Dri ll Bit Q&A
a small cuttings size across the various plug materials,
which limits hole-cleaning efficiency.
The Slipstream bit features a dual cutting structure
with steel tooth and tungsten carbide inserts (TCI) on
each cone for greater efficiency and less wear. The TCI
cutting structure is on the outer rows of the cone where
heavy wear occurs when drilling hard components. The
steel tooth cutting structure is on the inner rows to drill
the softer composite part of the plugs. The fit-for-purpose
inserts are subjected to a high-energy tumble (HET)
process to increase durability. Short and closely spaced
steel tooth inner rows are fully covered by DuraClad
premium welded hard metal to provide high durability and
small cuttings for easy transport. A seal gland design and
pressure attenuator along with a canister compensator
increase reliability by addressing pressure fluctuations that
occur when drilling out each completion interval.
Stabilityandvibrationresistance
SmartBox provides hi-res insights on downhole dynamics
A better understanding of downhole dynamics is being
achieved with a downhole measurement tool that acquires
a variety of drilling parameters at a high sample rate.
The recorded data is used for optimising bit designs and
operational parameters that improve drilling efficiency and
reduce rig time.
The tool is a small, standalone instrumented sub with
a maximum sampling rate of 100 Hz. The device captures
high-resolution measurements of dynamic, mechanical,
and hydraulic data such as vibration, torque, and
pressure. The sub is made up in the drill string near the
bit or in the bottom hole assembly. It has a battery life of
300 to 648 hours, depending on the sample rate.
Collected data are recorded and downloaded at the
surface using a laptop computer. A suite of software tools
process the data for different purposes ranging from the
analysis of bit and drill string dynamics, to investigation of
cutting structure design. In addition, the data is important
to assessing drilling equipment performance such as
monitoring motor torque and rotation speed, and evaluating
vibration severity. The tool is produced in three models to
provide maximum utility with common drill string sizes.
Tacklingdirectional drillingchallenges
The ability to drill Eagle Ford wells from spud to TD with
a single bit and bottom hole assembly (BHA) has been
achieved with a bit designed to optimally drill tangent,
curve, and lateral wellbore sections. The company’s
modified Voyager fixed cutter bit is eliminating trips as well
as associated motor and MWD costs to achieve significant
improvements in well economics.
Area wells typically require two to three trips to effectively
drill the wells, adding major costs in terms of trip time, and
changes to the BHA determined by formation and wellbore
geometry. In offsets, an average 4457.7 ft tangent section
was drilled in 29.8 hours at 149.58 ft/hr ROP; the average
curve/lateral section of 6780.6 ft was drilled in 104.9 hours
at 64.63 ft/hr. The three combined sections (11 238.3 ft) were
drilled in an average 134.7 hours at 83.4 ft/hr, but the addition
of an 18 hour round trip resulted in an overall offset average
of 152.7 hours and an overall ROP of only 73.6 ft/hr.
Eliminating the trip (plus BHA costs) had a significant
impact on performance. The first ten runs of the Voyager bit
used a single bit and BHA to drill all three sections, for an
average 12 125.4 ft, drilled in 120.8 hours at 100.38 ft/hr. In
addition to achieving significant time and costs savings, the
new bit has resulted in greater consistency in both drilling time
and wellbore quality for true ‘factory drilling’ performance.
The bit’s development necessitated detailed modelling
to balance the speed and durability required in the tangent
and lateral sections with the demand for steerability in the
curve section. Advanced algorithms, rock analytics, and
Figure 2.
The SmartBox tool measures downhole dynamics to
improve drilling efficiency and reduce rig time.
