Pohokura – another world record gas landfall for Lucas

The field is estimated to have reserves of 900 Bcf of gas and 50 MMbbl of condensate.

The project’s HDD landfall comprises three pipes: 324, 101 and 60 mm diameter, carrying multiphase product, chemical injection lines, power and optical fibre cables. These were installed in two HDD bores of 609 and 914 mm.

The drilled landfall crosses a 33 metre cliff and an offshore “˜reef’ which is actually pyroclastic flows from Mount Taranaki, the volcano that dominates the local landscape and which is scheduled to erupt in about 100 years. At 1,850 metres overall, this is the world’s longest HDD landfall.

The key challenge was crossing different geological layers. The underlying layer is fractured siltstone, locally known as “papa”, and above this is a mixed layer of sands, clay, volcanic cobbles and boulders. Finally, there is a metre of sand and gravel at the exit on the ocean floor.

To cross the surface layers of pyroclastic boulders and cobbles, a casing was hammered in 120 metres using a 2,000 tonne impact pneumatic hammer. This was the first job for Lucas’ new American Augers DD1100 rig. With 500 tonnes of push/pull capacity and
136 kNm of torque, this is the largest rig in the Asia Pacific, and among the five largest worldwide.

This was also the first time Lucas used a centrifuge to control the superfine cuttings from the siltstone and mud.

The project presented unique challenges for Lucas, and its successful completion was a significant achievement for the company.

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