BJ
Tubular Services’ composite drillable drive shoe improves
dual-use piles for 12-well platform offshore Borneo
Posted: 12 March 2004
BJ Tubular Services has completed a contract for Murphy Sarawak
Oil Company of Malaysia to provide pile-driving services for its
jackup-deployed platform installation off the west coast of Borneo.
The project proved to be a real engineering and operational challenge.
The four structure support piles – measuring 36in. x 1.25in.
– would also be used as conductors for the Production A Platform
in West Patricia Field. Each of the four structure piles –
or conductors – were to contain 3 x 13-3/8" casing strings,
utilising AB- STL flush connections depending on pipe weight. This
configuration would serve as the basis of a 12-well platform. The
four piles were made up using internally-externally flush Oil States
Puma connections.
Murphy Oil Engineering determined that the required depth –
or penetration - of the 36-in. piles would be from 72 to 75 meters
below mudline. Using soil data provided and drive simulations, BJ
proposed to use a reduced (ID) drive shoe to reduce the potential
for washing out the casing during driving to reach the required
pile penetration. This type of drive shoe is normally constructed
from steel and remains inside the tip of the pile after it is successfully
driven into place.
However, due to the risk of connection interference and/or hang-up
at the pile tip, Murphy Sarawak wanted a drillable drive shoe to
avoid a permanent reduction in pile I.D. As an alternative to conventional
approaches, BJ proposed using an insert made of material other than
steel that would perform the same function as a traditional drive
shoe, but could be removed after pile driving was completed. Called
the Composite Drillable Drive Shoe system (CDDS), this approach
would mitigate internal pile skin friction while driving and allow
installation to be achieved with currently available equipment.
BJ considered several different materials and methods of installation,
finally settling on 15mm thick composite material sheets formed
to suit the I.D. of the pipe in question, which were then bonded
to the inner bore of the parent pipe.
BJ designed inserts and constructed scale models before testing
them to destruction to determine the shear potential of the bonding
material. Once testing was completed, BJ proposed the new system
plans to Murphy Sarawak. The presentation included pile-driving
simulations to demonstrate the performance of the composite material
insert in conjunction with BJ’s specialised Offshore Hydraulic
Pile Driving System.
Murphy Sarawak agreed to the use of the removable composite material
insert, and BJ commenced with fabrication and subsequent installation
of the inserts. The approach involved removing the insert after
pile driving had been completed during the first pass of drill bit,
while the combined structure pile/conductor string was cleaned out
to a point located just past the shoe. A watermelon mill was located
above the bit and set to the I.D. of the pipe at 33.5". By
doing so, the tip of the conductor/structure pipe size is returned
to the size of the parent bore. Drilling forward then commenced
for the 3 x 13-3/8in. casing strings, and was successfully completed
on schedule.
"The greatest challenge for us was to devise an easily extractable
drive shoe that would deliver the same performance as the standard
steel unit, but could then be removed permanently from the pile
tip. The composite material insert performed well, as indicated
in our field testing and pile driving simulations," said Doug
Bell, area manager – Asia Pacific for BJ Tubular Services.
"The primary benefit of this approach is that when we remove
the drive shoe, we lower the risk of possible connection problems
and complications at the pile tip sometimes caused by permanently
reducing the pile I.D. By preventing these problems, the overall
operation is likely to run more efficiently. In the long-run it
will be less costly," he added.
BJ has successfully carried out several pile driving operations
in Malaysia using the CDDS. Looking ahead, BJ will be carrying further
similar procedures for operators in Malaysia and Vietnam.
For more information see www.bjservices.com
Posted by Richard Price,
Editor Pipeline Magazine
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