American Oil and Gas Reporter - January 2012 - 146

quality well bore, minimizing back reaming
time and improving completion operations.
Because of the unique design of the system,
it can be seamlessly programmed down
hole to drill a smooth, controlled lateral
with minimal tortuosity after completing
the curve section with an HBUR.
Because of the complex interaction between many technological and environmental
factors, the design of the HBUR RSS required a comprehensive consideration of
the entire system, including the BHA, drill
bit, drill string, and eventually the drilling
fluid, to achieve predictable results. Based
on targeted bit features, three-point geometry
and engineered BHA stiffness, the HBUR
RSS has delivered BURs greater than 17
degrees/100 feet in test applications, significantly higher than what was required to
achieve the planned well profiles of the
four Devon-operated horizontal Granite
FIGURE 2

Wash wells discussed in this article.
Design application review teams
(DARTs) have been implemented to design
or modify system-specific bits for each
new area in which the system is introduced
to enable optimum performance in each
application. This interdisciplinary, crossfunctional team approach, which includes
drill bit and drilling system research engineers, design engineers and applications
engineers, has proven to be very effective
at ensuring the goals and objectives of the
entire system are met.
The process includes reviewing dull
conditions and performance from recent
offsets, utilizing sophisticated software
drilling models to review potential performance and stability for a system-specific
bit and cutter type, and laboratory evaluations
for model verification.
The drill bit used in these Granite Wash

Drilling Performance (Four Case Study Wells)

0

Total Hours
40

20

60

80

0
200
Footage Drilled [ft]

POOH caused by not
meeting required BUR

400
600
800
1,000
1,200
HBUR Curve #1

HBUR Curve #2

Bent Motor-Field Benchmark Curve (6.18 miles)

Offset Curve #1 (1.34 miles)

Offset Curve #2 (1.39 miles)

FIGURE 3
Drilling Performance (Different Granite Wash Field)
0

10

20

Total Hours
30

40

50

60

0

Footage Drilled [ft]

200
400
600
800
1,000
1,200
HBUR Curve #3

Bent Motor-Field Benchmark Curve (3.25 miles)

Offset Curve #1 (0.80 miles)

Offset Curve #2 (1.10 miles)

Offset Curve #3 (1.75 miles)

146 THE AMERICAN OIL & GAS REPORTER

case study wells was specifically matched
to the new three-point geometry of the
steering tool. This 83⁄4-inch PDC bit (IADC
code M223) incorporates 16-millimeter
cutters on six blades with 13-millimeter
backup cutters. Its gauge is shaped to
achieve the required bit tilt angle to provide
the correct amount of lateral aggressiveness
to ensure proper BURs.
It also is designed to reduce unwanted
high local doglegs and to facilitate good
hole quality with minimum surface roughness (which can result from overly aggressive
side cutting). Achieving the proper dogleg
without causing increased torque generally
results in minimized reaming time and reduced nonproductive time. An optimized
cutting structure ensures high penetration
rates while also providing good bit stability
and reduced dynamic dysfunctions.
Granite Wash Case Study
All four of the Granite Wash wells in
Wheeler County, Tx., were planned with a
BUR of 10 degrees/100 feet in the curve
section, with section lengths of approximately
1,000 feet measured depth. The performance
of the HBUR RSS was measured against
the fastest field benchmark drilled with
motors, and other offset wells drilled in
close proximity (curve sections previously
could not be drilled with RSS technology,
only the lateral sections).
Figure 2 shows time versus measured
depth curves for field A, normalized to the
kickoff point of the curve. The best steerable
motor run in the field finished the curve in
44 hours, while offset wells in close proximity required 51 hours and 86 hours for
the curve section to reach total depth. In
the latter well, a round trip was required
after the first assembly failed to meet directional requirements. The HBUR RSS
successfully drilled two wells significantly
faster than the steerable motor field benchmark. Both curves were finished in less
than 40 hours. Compared with the field onbottom ROP average of 23 feet/hour, the
HBUR RSS delivered improvements of 53
percent (35.5 feet/hour) and 36 percent,
respectively.
While the wells were planned for 10
degrees/100 feet build rate, it was desirable
to stay ahead of the curve to have some reserve for corrections while still landing the
well on target in case the directional results
could not be met in all parts of the application.
The HBUR RSS delivered reliable BURs
in the range of 11 to 12 degrees/100 feet,
safely meeting well plan requirements.
Figure 3 provides a similar comparison
for a different field in Wheeler County,
where the HBUR RSS drilled the curve at
40.09 feet/hour, providing a 78 percent
ROP improvement versus the field average
for the operator. It also drilled with 35
percent faster ROP than the field benchmark
using a bent motor. Build rate requirements
American Oil and Gas Reporter - January 2012

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