Installation Of Four Through Leg Piles In 81m Of Water

LDD uses experience and innovation to achieve success on first project.

Large Diameter Drilling Ltd’s (LDD) first project was to drill and grout the 42-in. tubular piles for a jacket installation for VAALCO Gabon (Etame) Inc. in Ebouri field, offshore Gabon.

Using newly acquired and fabricated equipment, some of which it developed specifically for the project, LDD installed four through-leg piles raked at 1:8 and 1:10 batter in 81 m of water.

LDD was awarded the contract, worth $2 million, following a meeting with VAALCO Energy (VAALCO) in Houston in December 2007. Andy Seager, operations manager, LDD, says, “We walked out of VAALCO’s office totally elated, but there was a lot of work to do, as we were expected to be in the field drilling in six months.”

The newly formed LDD started work on planning and building the specialist equipment that would be required for this and future projects. Seager says, “From our experience, we knew the biggest challenge was likely to be working from a floating construction vessel onto a fixed platform on the seabed and dealing with the vessel heave motions and forces.

These would be particularly problematical when inserting and withdrawing the bottomhole assembly, as there is only 1.5 in. of radial tolerance when the drill bit is run through the centre of the pile. This meant that there was potential for the drill to get caught on withdrawal or to touch the base of the pile and damage either the pile itself or the system that attaches the drill rig to the top of the pile when running in.

LDD developed a solution – a passive heave compensator with a 3-m stroke for safe working loads up to 60 t to negate the potential point loading and snagging impact. Using this device, they were able to reduce the point loading to just under a tonne.

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