Ekofisk City, How it was done

(Chris) #1

This is a description of how Ekofisk City was created back in the 70’s. Since it’s pretty much in a un-hospitable part of the North Sea, and was created with 70’s technology, I thought it might help anyone like me that tends to get discouraged by some of the engineering problems.

10 months out of the year, this place has pretty rough seas with winds up to 150 knots. It’s got a hotel and a hospital to support the nearby wells. Yes this was an investment of billions of dollars, but given the nasty location and the breakthroughs since then, it offers encouragement to us in my opinion.



Hard to call an oil tank a “city”. I could have sworn that tank was removed in the late 1980’s, when pipes to the mainland were installed.

I remember some large concrete tank was removed back then. It was difficult from what i recall.





(Chris) #4

It was removed about a decade ago I believe. The tank was used for a long while even after the pipelines were put in place.

It wasn’t just a tank, it had two stories above the tank that had the hotel hospital, communications center, helipad, and a bunch of other stuff. Even at 130 ft above the water it still got rogue waves that hit the top deck.

Pretty amazing engineering in my opinion.


So, basically they built a giant floating spar, downward, until it reached the sea floor, then built up another 130 some ft and used it as an oil storage tank?

Sounds like what I’ve been trying to describe doing, on smaller scale, in several threads…

(Chris) #6

The first stage, which was basically the tank, was built and floated there. It was filled to sink it and the rest was built on top of that. (Slip-formed I believe as it sank.) One of the reasons that removal was difficult was because they couldn’t just empty the tank or would have been crushed under the outside pressure. I think they disassembled what was above water and just cleaned the tank and left it in place.


Almost the exact same thing I’ve tried to describe…

Start with a barge full of supplies and what-have-you, with a formed opening in the center, make a bottom and slip-for downward, then start ballasting it, while continuing to slip-form downward, adding baffles and plumbing as you go.




(Chris) #8

Stability wise, that seems to be a winner. Having a solid structure to ring breakwaters around makes things easier too. I am leaning this way as well, but I have changed my mind on structure many times.

(system) closed #9

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