Fully enclosed, atmospheric-pressure working environments are to be built on the seafloor to help maintain and perform intervention operations on the fast-paced, deepwater subsea production systems of the future.
At least that was the plan in the mid-late 1970s. High oil prices were driving investment in technologies which could enable production from what was then considered deep water and out of diver range. The one-atmosphere system was one of the hot topics at Bergen’s second ever Underwater Technology Conference (UTC) in 1982, the papers from which, along with the 1984 – 1996 UTC proceedings, have now been archived online.
The archives offer a fascinating glimpse into the history and development of subsea technologies – and why they succeed and fail. The one-atmosphere system was a logical idea, to transport operatives from support vessels to enclosed, dry-tree, one-atmosphere working environments, on the seafloor via an adapted diving bell type system.
While it might sound – and look – like something from science fiction, the idea was a success. In 1979, first production started from a nine-well dry, one-atmosphere system, built and installed for Petrobras on the Garoupa field offshore Brazil as an early production system, by Lockheed Petroleum Services, which became CanOcean.
But, another concept, underwater robots, which also seemed like sci-fi in 1982, were emerging at the same time, and fast. A whole section of the 1982 conference, held at the SAS Royal Hotel in Bergen, was dedicated to remotely operated vehicles and their potential for underwater operations and intervention, such as Myrens Verksted’s Snurre ROV, developed with the Continental Shelf Institute in Norway. ROVs were still rough, limited in application, and still very much a technology of the future. But, their potential, and the development of wet-tree technology, was enough to overshadow one-atmosphere systems.
Ernie Sjoholm presented CanOcean’s system at the 1982 UTC. He’s now retired, living in Richmond, Vancouver. He reflects: “The whole logic behind one atmosphere assumed it was not cost effective to operate beyond diver depth. That is where it came into its own, but then underwater robotics came and stole the show. It is a smarter way of doing it, I have to admit that. At the time, in the late 1960s, when the (one atmosphere) concept was first tabled at Lockheed, it seemed like the smart way to do it.
“When remote pulling in of lines into drilling templates and setting and retrieving control pods remotely came along, the one-atmosphere system just wasn’t viable anymore.”
Lockheed Petroleum Services’ parent company had developed submarine rescue systems, using the same technology, i.e. landing on a submerged one-atmosphere container, pumping out the water from the connection to create a one atmosphere door to let people in or out. “The natural progression was to say you could put the Xmas tree in the submarine and the you can send a normal guy down with onshore experience,” says Sjoholm.
Shell, Texaco and Union Oil dabbled with the one-atmosphere idea in the Gulf of Mexico, installing shallow water test installations, and Burma Oil considered it for the North Sea. In 1973, Petrobras leaped into the deep and signed up for the system for the 400ft deep Garoupa field. While the water depth didn’t prohibit a platform (a platform was built later on the field), Petrobras was keen to get early production and it was willing to spend some US$200 million to develop the system, says Sjoholm.
“In the early days of the 1970s there was a need to come up with a way to produce when you get out to 1000-2000ft water depth,” he says. “Everyone was interested in doing that. The companies wanted to test it on small shallower fields. CanOcean went from about 12 to 400 staff after the order, says Ernie. They were heady times.
“There was some pretty novel sealing technology involved and we needed of course to pull in pipelines into these chambers and seal them,” he says. Lockheed used large volume submersible pumps and a breathing system developed for space travel – effectively routine equipment, says Sjoholm.
A system for up to 4000ft had been under consideration by the firm, which at that time would have covered all known developments in the Gulf of Mexico, North Sea and most of Brazil. But it was not to be. “By that time the industry was totally committed to putting down templates and completions remotely,” says Sjoholm.
“It was an interesting chapter in developing subsea oil and gas production, but a chapter that closed logically and essentially for good reason. You never know, things like this system maybe could influence future projects. You need to know your history to look forward.”
You find Sjoholms paper at page 101 in the 1982 proceedings.
Written by: Elaine Maslin, December 2014
To access the archive and view papers presented at UTC 1982 – 1996, click HERE