Case study
SHARC PDC Bit and PowerDrive Archer RSS Save
Operator USD 9.8 Million Offshore Australia
Precise directional control reduces sidetracking improves borehole quality
Challenge
Drill high dogleg borehole with PDC and
RSS drilling system, reduce the BHA’s
tendency to drop inclination through the
unconsolidated reservoir sand offshore
Australia.
Solution
Use IDEAS* drillbit design to modify a
standard SHARC* PDC bit by optimizing
the drillbit blade count, cutting structure
exposure, and nozzle configuration, and
pair it with a PowerDrive Archer* RSS to
accomplish the operator’s objectives.
Result
The SHARC bit and PowerDrive Archer
RSS to consistently held inclination
through the drop zone and drilled horizontally in a high ROP environment. It
marked the first time a PDC and RSS were
combined with this result. Increased directional control reduced sidetracking and
improved wellbore quality. This enabled
a quick screen deployment saving the
operator USD 9.8 million.
High-build rate RSS with systemmatched PDC bit required
The operator is using extended reach
horizontal drilling techniques to develop
lower Cretaceous oil reserves offshore
Australia. During the initial phases of the
drilling campaign, the operator was forced to
construct a 9½-in section with a bent angle
positive displacement motor (PDM) drive
system to deliver the dogleg requirements
and effectively geosteer in the reservoir. PDM
drilling proved costly and time consuming,
resulting in poor and tortuous borehole, which
limited horizontal reach. The operator experimented with two different rotary steerable
systems with limited success. The major issue
was the inability of a standard dogleg RSS to
maintain wellbore trajectory drilling through a
drop zone composed of unconsolidated reservoir sand. This required expensive sidetracking
to correct wellbore trajectory, a conventional
PDM BHA or both to reach TD. In some cases,
another trip was needed to continue drilling
with a RSS. Rollercone tungsten carbide insert
(TCI) drill bits were used because of rig torque
delivery limitations, but a three year design
initiative resulted in several new TCI footage
and ROP records.
Drilling strategy: Phase III
Before launching Phase III development, a
team of well construction professionals brainstormed specific drilling operations to determine areas for potential improvement. The
plan was to design a drilling system that would
provide precise trajectory control and the
capability to drill the drop zone without sidetracking or tripping for a BHA change out. The
team concluded that the PowerDrive Archer’s
RSS high build-rate capability could solve a
multitude of application issues associated with
PDM drilling systems. The PowerDrive Archer
dogleg capability would enable it to cross drop
zones and steer through obstacles that proved
difficult for standard RSS.
SHARC MDSi716 8½-in drill bit with two rows of
cutters in the critical shoulder area provides maximum
durability in abrasive formations.
Drill Bits
MD interval other bit, m
MDSi716LKUBPXX
(4-6-BT-A-X-I-CT-TD)
MDSi716LKUBPXX
(4-5-BT-A-X-In-ER-TW)
MDSi716LKUBPXX
(2-6-BT-S-X-2-ER-TD)
MDSi716LKUBPXX
(3-5-BT-S-X-In-CT-BHA)
MDSi716LKUBPXX
(2-6-BT-S-X-IN-CT-DTF)
MDSi716LKUBPXX
(8-7-RO-C-X-2-BT-TD)
MDSi716LKUBPXX
(3-6-WT-A-X-1-BT-PR)
MDSi716LKUBPXX
(1-7-BT-S-X-I-CT-TD)
MDSi616LBPX
(3-3-CT-A-X-IN-BT-TD)
MDSi716LKUBPXX
(1-5-BT-S-X-1-LT-PR)
MDSi716LKUBPXX
(1-3-CT-S-X-I-NO-TD)
MDSi716LKUBPXX
(4-4-CT-A-X-IN-ER-TD)
9 ½-in Other PDC
(1-6-BT-S-E-I-ER-TD)
9 ½-in MDi616LABPXC
(1-1-CT-S-X-I-ER-BHA)
MD interval Smith Bits, m
On-bottom ROP, m/h
90
2000
Interval Drilled (m)
100
2200
80
2400
70
2600
60
2800
50
3000
3200
3400
3600
3800
Average meterage
drilled per run with
PDC on RSS 1 =
98m, with poor
directional control
4000
40
Average meterage
drilled per run with PDC
on RSS 2 = 371m, with
poor directional control
4200
30
ROP (m/h on bottom)
1800
9½-in Other PDC
(2-4-BT-S-X-I-NO-BHA)
Other PDC
(0-1-CT-S-X-I-NO-TD)
MDi616CTPX
(1-1-BT-A-X-I-ER-BHA)
1600
MDi616CTPX
(1-1-PN-N-X-I-ER-BHA)
Case study: SHARC PDC drill bit and PowerDrive Archer RSS improve directional control, Australia.
20
Average meterage drilled per run with PDC
on PowerDrive Archer = 970m
10
0
4400
Phase I
Phase II
Phase III
Evolution of project from Phase I to Phase III showing 10x increase in meterage per run with SHARC MDSi716 and PowerDrive Archer drilling system
The solution would provide all the traditional advantages of using RSS
including enhanced wellbore quality, better hole cleaning and more
effective geosteering in the reservoir. However, the new BHA would
require a system matched PDC bit with proper blade count and cutter
configuration to ensure optimal directional response and drillstring
stability. Other changes included a switch to water based mud, a reduction in hole size to 8½-in and rig modifications to provide the required
torque to efficiently drive the SHARC high-abrasion-resistance PDC drill
bit and bottom hole assembly.
Engineering assessment
Since most of the offsets were drilled with a rollercone and PDM
assembly, only six applicable PDC/RSS runs were available for
analysis. A dull grading exercise revealed bit body erosion caused by
cuttings recirculation and vibration induced cutter chipping. Any new
PDC design would need to address these issues. Relying on limited
data could prove problematic and force the operator into a trial and
error approach to develop a matched PDC bit. To avoid field trials,
designers used IDEAS drillbit design platform to evaluate several
different PDC cutting structures in a virtual environment that matched
the operator’s application to determine which base design offered the
best combination of directional responsiveness, high ROP potential,
and stability for the directional profile and formations to be drilled.
Over 200 simulations were run, after which iterative changes were
made to the bit resulting in the final 8½-in SHARC MDSi716LKUBPXX
design. Specific modifications include:
■■
diamond-impregnated depth-of-cut control feature to reduce
torsional vibration/ensure blade top durability
■■
CFD* modified hydraulic layout to mitigate cuttings recirculation
■■
high-erosion resistant matrix bit body
■■
modified gauge pad length with diamond protection
Integrated tool solution produces win-win scenario
The application of the IDEAS designed SHARC bit on a
PowerDrive Archer RSS successfully delivered the required directional work on the two wells/five laterals and consistently corrected
inclination even while drilling the extreme drop zones where ROP
reached 300 m/h. This was also the first time the PowerDrive Archer
RSS was used in deepwater to geosteer horizontally in a high-ROP
application rather than just for its ability to drill short radius borehole.
The improved directional control and well placement capabilities
eliminated the need for drop zone correction sidetracking. The BHA
delivered a smooth high-quality wellbore significantly reducing the
time required to run openhole sand screens. This increased operational efficiency saved the operator USD 9.8 million.
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