Silence is a seldom-heard bird on any sea-going vessel. Pursuit of its elusive song occupies the free time of new sailors, but all too soon they learn that there is a price to pay for capturing five minutes of quiet. The purr of the diesel engines creates a gentle humming vibration that, when combined with the sway of the vessel to and fro, becomes a sweet bedtime lullaby. Replace that with silence, and the dream quickly becomes nightmarish as it indicates trouble below deck. A vessel without power is a dangerous place to be.
So it had to be more than a little unsettling for the crew of the Maersk Invincible on May 28 when the jackup’s diesel engines grew silent but the rig remained running on hydropower supplied by shore via 294-km (183-mile) high-voltage DC cable that runs from Lista to the Valhall Complex in the Norwegian North Sea, where the harsh environment rig is on station.
“This is a pioneer project for Aker BP. Electrifying the drilling rig allows us to significantly cut local CO2 and NOx emissions,” said Per Mikal Hauge, Valhall field director for Aker BP, in a press release. “This is in line with our strategy of developing solutions that contribute to minimizing the environmental consequences of our activities.”
Calculations show, according to the press release, that electrification of the drilling rig will reduce local emissions by 15,200 tonnes of CO2 and 168 tonnes of NOx every year.
Production from the giant oil field’s chalk reservoir started in 1982, with production passing 1 Bboe in early January 2017, according to Aker BP. The field underwent an extensive redevelopment project that was completed in January 2013. Along with the installation of the shore power system and cabling, a new processing/ hotel (PH) platform mounted on a fixed steel jacket, an external system of bridges and walkways linking the PH to the existing complex, new subsea pipelines and more were installed, according to Aker BP.
The Maersk Invincible operates under a five-year contract to Aker BP to perform well plugging operations on 18 wells from the Valhall drilling platform, according to the company.
The newly built rig arrived onsite in early May after an extensive transit from the Daewoo Shipbuilding and Marine Engineering shipyard in Okpo, South Korea. The jackup is the fourth and final of Maersk Drilling’s XLE line and is considered to be the world’s largest jackup, according to a Maersk press release.
The rig was purpose-built for this project since the electrical power system was designed and prepared to receive power from shore, the release stated. At 11,000 volts, the high-voltage shorepower supply is capable of supplying up to 10 MW, corresponding to the consumption of up to 20,000 households, the release stated.
The innovation not only means reduced emissions but also a cost savings for Aker BP in fuel and maintenance, according to Maersk. Another benefit of shore power is a much quieter work environment for the crew since the diesel engines were one of the main sources of noise.
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