Imagine that Poseidon, god of the oceans in Greek mythology, didn’t much care for your offshore project, even after the plans were checked, the financing came through and the lawyers signed off on it.

Imagine he sent tough weather to the Cape of Good Hope to slow the ship transporting your moored turret buoy, then unleashed a 161-km-wide (100-mile-wide) sea monster into the Gulf of Mexico (GoM) as you attempted to install your FPSO unit.

You could text Odysseus to see if he’s available for a freelance gig or, like Shell, rely on a team of smart engineers determined to figure out a way to install the Stones FPSO unit, the world’s deepest project of its kind at 2,896 m (9,500 ft).

Or you could just read the paper “Offshore Construction—Installing the World’s Deepest FPSO Development” delivered by Carl Webb, Shell’s turret and installation lead for Stones, at the May 2 afternoon technical session.

LISTEN: Hosam Abu Zeid, Schlumberger, talks about the the Stones FPSO unit.

Seemingly everything about this project was of Olympic proportions. It literally took a Herculean effort (the vessel’s name is Asian Hercules III) to hoist the 3,200-mt buoy and move it from Keppel’s Benoi Yard in Singapore to the heavy transport ship Swift for the 46-day journey to the GoM. A two-day delay to avoid severe weather and other delays at the fabrication yard stretched the trip to 55 days.

In the GoM, Swift joined deepwater construction vessel (DCV) Balder and DCV support vessel Union Manta, along with barges and tugs. The installation plan was straightforward:

  • Install nine mooring suction piles;
  • Assemble the mooring lines and connect them to the suction piles;
  • Offload the buoy; and
  • Attach the buoy to the mooring lines and have the system properly submerged and ready for the FPSO Turritella’s arrival.

That’s when things got weird.

Typically, warm water loops the GoM to the east and merges with the Gulf Stream on its way to Europe. But in 2015, inexplicably, that warm water broke off and spun west, creating vast circular eddy currents that grew to more than 161 km in diameter, with depths of up to 300 m (984 ft).

The swirling waters meandered into the steam above the Stones Field, bringing currents of 3.5 knots. Installation activity stopped because the ROVs conducting the work cannot function in currents faster than 1.8 knots.

So the flotilla waited for the eddy to clear so it could get to work. Sometimes the eddy would retreat for periods of six to 24 hours. Sometimes it would drift 1.6 km (1 mile) away and sometimes as far as 16 km (10 miles). Once it hung out directly over Stones for three straight weeks.

In bizarre irony, the ships were exactly where they needed to be but the sea itself was lost, unable to find the Gulf Stream.

So the crew tracked the eddy’s movements from reports off of an eddy boat traversing the GoM, studied its pattern and predicted the next retreat of 24 hours or more. They needed enough time to hook up at least three of the moorings. That would be enough to secure the system.

“If the operable current windows are too short, we’re going to be taking too much risk, and I don’t want to get into a position where we have one or two mooring lines connected when the current hits,” Carr said in an on-location video shown during his presentation. “Where I want to be is at the start of the operation and be in a position to finish it or just don’t start.”

Carr made the call to go ahead, the eddy remained at bay, so to speak, for enough time to connect the nine mooring lines and in September 2016 Stones produced first oil.

For Carr, the key lesson learned was what was needed when working under pressure: competence, discipline and agility. Out in the middle of the GoM, conditions forced changes in the original plan and the offshore engineering team from Heerema Marine Contractors and Shell were up to the challenge.

An eddy can wander a body of water for years. The one that disrupted the Stones installation is still in the GoM, though weaker. And like hurricanes, they are named.

This one’s name? Olympus.

Joseph Markman can be reached at jmarkman@hartenergy.com or @JHMarkman.