Challenge: Drill 17 1/2-in tophole section of deepwater well from vertical to inclination of 50° in soft formation while maximizing ROP and ensuring high borehole quality.
Solution: Build angle with BHA incorporating
Shell Brazil had been drilling deepwater wells targeting reservoirs located 1,000 m or less
below the mudline. To drill the wells’ reservoir sections horizontally, it was necessary to build
angle in their tophole sections, which was difficult because the formations were soft and
unconsolidated. Tophole sections of the initial wells were drilled with motors and 16-in tricone
bits. These BHAs were sliding two-thirds of the time—limiting average ROP to about 10 m/h—
and could only achieve inclinations between 21° and 36° by section TD.
In later wells, the tophole sections were drilled with BHAs incorporating a 9-in PowerDrive
Xceed rotary steerable system (RSS) for harsh, rugged environments, a 12 1/4-in polycrystalline
diamond compact (PDC) bit, and a 17 1/2-in under-reamer. These BHAs eliminated the need for
sliding, increasing average ROP to about 35 m/h, and delivered inclinations of 25° to 40° at
section TD. Shell Brazil wanted to further improve drilling performance to achieve an inclination
of 50° at section TD while maximizing ROP and ensuring high borehole quality.
Schlumberger met Shell Brazil’s objectives
by incorporating best practices and lessons
learned from 9-in PowerDrive Xceed operations
worldwide and taking full advantage
of the RSS’s large-hole DLS capabilities.
Extensive modeling and simulations of
BHA tendency, hydraulics, and torque and
drag, together with the lithology directional
tendency in the area, were used to select the
most efficient set of drilling parameters, the
proper type of bit, and the hydraulic horsepower
per square inch (HSI) required. As part
of the integrated solution, Smith Bits and M-I
SWACO conducted risk analysis and modeling
to help determine the best borehole stabilization
profile, BHA design, bit HSI, and hole
In addition to the PowerDrive Xceed RSS, the BHA included a 17 1/2-in XR+VE3JPS tricone bit,
which improved hole cleaning by eliminating the need for an under-reamer. The BHA also
included an arcVISION825 8 1/4-in drill collar resistivity tool, and the TeleScope high-speed
telemetry-while-drilling service. The arcVISION825 tool provided array compensated resistivity
and APWD annular pressure-while-drilling measurements that were sent to the surface
in real time by the TeleScope service, along with vibration and IWOB integrated
Despite the soft, unconsolidated formation, the point-the-bit PowerDrive Xceed RSS achieved an
inclination of 49.7° at section TD, with an average DLS of 2.4°/30 m. ROP averaged 45 m/h and at
times reached 80 m/h. The high-quality borehole enabled the drillstring and BHA to be tripped out
of the hole with minimum drag and the 13 3/8-in casing string to be run to bottom. This performance made this PowerDrive Xceed BHA the front runner for upcoming campaigns involving eleven 17 1/2-in tophole sections and for development of a potential field to produce a relatively shallow reservoir roughly 700 m below the mudline.
Download: Shell Brazil Achieves High Inclination in Soft Formation (0.92 MB PDF)