Bergen, Norway 11 – 13 June, 2019

Man vs ROV: Offshore operating costs compared

Inside knowledge on what might be regarded as one of the most glamorous and possibly well paid offshore jobs will be shared by professional expert at this year’s UTC conference. Rolf Røssland, managing director of NUI  AS, the subsea intervention testing and training centre at Laksevaag just outside Bergen, is due to argue for the  relevance of manned diving in the current cost-conscious oil price environment.

With a presentation that is due to discuss manned underwater intervention in suitable water depths,  Rossland will share some of his expertise built up over years in an industry segment which has changed much from the early days of the “pioneers.”

While remotely operated vehicles (ROVS) operations have dominated in deepwater, and have also been deployed shallow water, Rossland will argue that manned diving still has its place in today’s energy industry and can sometimes be a better intervention solution.

“It is not about ROVs against diving. The issue is about finding the most cost effective intervention method for the job to be done,” he says.

One of the advantages of manned diving over ROV operations is the adaptability of the diver, says Rossland. Divers, he says, can work more effectively in the time available under water. “An ROV which is remotely operated with a joystick is quite a challenge – to connect two flanges or to get to a valve for example. It will take the ROV much longer to connect the special designed clamps with special tools than for the divers to connect it with ordinary bolts and standard tools. A diver is more flexible. He can also use standard tools for most work and he can work in a confined space.

“The limit for divers is basically depth. An ROV can get to thousands of metres. It can stay in the water. And it can go deeper with no physical limit.”

Diver - ROV (002)


An ROV can easily fly around a platform for a subsea inspection: “The point is not whether to have manned diving or not, but whether it is the best intervention method for the job,” Rossland points out. “It is often significantly cheaper to do some jobs with divers. You do not have to have fancy or specialised equipment that an ROV needs: For example tools – the divers can use “off the shelf”  tools and equipment that for an ROV have to be specially designed.”

He also emphasises the long term planning required for ROV work, which can sometimes be two – three times longer than for manned diving and involves much more resources. If ROV work requires special tools or equipment, the planning process might even be longer. “And if you have to develop  site-specific equipment then you have to store and maintain it for the field’s lifetime.

“There is still a place for manned diving, but it needs to be considered as a method early in the planning. Some engineers will be sceptical about diving because they want to play with fancy equipment, but we assume that the ‘bean counters’ would prefer the most cost effective method.”

Rossland says there are lots of examples where a diver can accomplish a subsea task more cost effectively than an  ROV, and several examples will be presented at UTC.

“The only reason we dive, is that it is the most efficient way of doing the work.”

Manned diving has featured in the North Sea since the late 1960s. A low point was in November 1983, when five men died in a diving bell on board the Byford Dolphin rig. Four were in a compression chamber and a fifth was outside when the chamber was explosively decompressed. Another report indicates 17 divers died between 1967 and 1987.

“Based on the old safety statistics and the new ROV technology some of the Norwegian Operators decided to stop diving,” says Rossland. But times have moved on, equipment and procedures have improved and the safety statistics for offshore diving are now excellent.

“It is not dangerous to dive. The PSA (the Norwegian Petroleum Safety Authority) confirms that on their homepage,” adds Rossland. “If you accept to do work with people, you can dive, but you have to perform it the right way. We have an extreme focus on safety when you put people in the water.”

Manned diving still regularly takes place: “On  the NCS there are ongoing diving operations as we speak.”

There is plenty of history from the early days of the North Sea oil industry and its first, pioneering  deep-sea commercial divers.  Actor George Clooney is now  making a new version of a Norwegian film about those early days, called, “Pioneer.”

 One of those pioneers was Angus Kleppe, who worked offshore Norway. He has talked of professional pride among divers about going deep: “The Norwegians had the record – we’d gotten down to 500 meters [1,600 feet] – and there was an enormous amount of professional pride that came from that. We wanted to be able to keep it up,” he told the website during an interview discussing Clooney’s film plans.

Today there are too many older divers, Rossland accepts, and now diving companies are aiming to recruit younger people, to counter-act this. Few women have attempted to enter this part of the industry and those that have done so, have faded out, he says. “There is a lot of construction and air diving, but the saturation diving involves living in saturation chambers where you are very very close for weeks. The challenge is for the boys …when you are spending three, four five or even six weeks in a chamber, you are very living very close,” he explains.

Today’s diving industry is closely regulated too. Technology has changed: “There has been a significant improvement, both in equipment, procedures and competence,” according to Rossland. Previous incidents have encouraged a much greater focus on safety and today’s safety statistics in the North Sea prove that it has been successful, he argues.

In the North Sea today men may work in the water for between four and six hours. One can be in a diving bell and two others in the water. In one recent operation with a new vessel, Rossland says four men worked at a time — one in the diving bell and three in the water. Working with ROVs effectively optimises the use of a diving spread compared to the old systems that only allowed one diver at work at the time, according to Rossland.

Diving beyond 300 metres (990 feet) was common in the early days. Today, Rossland says it is usual for North Sea divers to operate down to 225 or 250 metres (740 – 820 feet). In Norway, 180 metres (590 feet) has been a limit.

“The limit is the physiology of the divers,” Rossland explains. “The breathing equipment is also an important part of the equipment and depending on depth, a change in the breathing gas, and the breathing apparatus might be necessary.”

Operating modern DSVs is expensive, he says, and the rate varies depending on the vessel and the job. A more sophisticated vessel is more expensive. “Today’s DSVs are also equipped with sophisticated ROVs and with a little planning, the efficiency will increase and the costs go down.”

“Statoil is one of many operators which is now saying you should use the intervention system that is the most cost effective for the job – it is not a case of either or…”


Written by John Bradbury