Maintaining Atlantis

As the offshore oil and gas industry moves to ever more remote locations to find competitive sources of energy, a considerable challenge is emerging in maintaining the complex operations they set up.

“Most of the easy offshore oil has gone,” says Anders Husby, head of the well, subsea and risers department at oil and gas consultant DNV GL.

“The industry is looking in deeper and harsher environments that need more processing equipment to be able to produce oil. Subsea pumping and compression is required to increase the pressure and get the fluid to the surface.”

You can’t go back to shore once you’re on site, so you need lots of equipment in case something breaks

Sebastian Hartmann

Separation technology is also installed in some cases to clean the material produced before it is pumped to the surface.

Statoil began operating the first advanced subsea separation system in Norweigan waters in 2001, with equipment installed for its Troll development on the sea bed some 340m below the surface.

Although only a handful of deep sea oil fields have so far followed on, experts expect a rapid acceleration.

“The industry is developing and there will be an increase in subsea processing,” predicts Husby confidently.

Each development is sizeable as well – there being little point going to the trouble of setting up processing plant in such inhospitable places without the capacity to produce large amounts of energy.

“There can be about 1,000 tonnes of equipment in one deep sea processing field,” says Husby.

Setting up such developments is one thing, keeping them in working order is quite another. And there is little room for error.

Sebastian Hartmann, sales and business development manager at marine inspection specialists Innospection, says: “The worst scenario for pressurised systems is a loss of containment.

“This would mean oil in the sea, which would be a loss of production. If the spill is reported, a production system could be shut down meaning an even bigger loss of production as well as a big loss of reputation. Oil companies don’t want to be in the media for something like this.”

It is not just the oil-carrying plant and pipework that need to be fully maintained though.

“Structural degradation could lead to something falling off a platform and damaging pipelines, causing the same scenario as described,” warns Hartmann.

So how do the oil and gas producers ensure that equipment far from the human eye is not going to cause them catastrophic problems?

DNV GL principal consultant for subsea operations Bente Helen Leinum says it is essential for companies to think about maintenance from design stage of new subsea oil fields.

“These deep subsea fields have big, complex plant,” she says.

“The main challenge is planning for maintenance from the beginning. We have been involved in extensions to existing fields where data is not good enough. To avoid that scenario, it is important to plan ahead and think about the type of dynamic equipment that will be used to maintain plant on the seabed.”

This means ensuring schemes are designed with spaces around equipment to allow cameras and remote tools to operate.

Consideration must also be given as to what can be built into the plant to remove the need for intrusive examinations.

“Engineering companies are working to understand the parameters so they can monitor equipment with sensors to detect leaks and other problems,” says Leinum.

Beyond this, companies need to be as prepared as possible for known risks.

“There are threats from ships passing, from fishing for example, and you need systems to minimise that threat,” says Leinum.

“Integrity management systems should include repair plans such as systems and spare parts.”

Third party expertise can be useful. DNV GL draws up best practice maintenance and disaster avoidance guides as well as running training courses and consulting on specific company plans.

However, periodical maintenance remains necessary no matter how forward thinking the design and tight the planning.

Such maintenance is a huge undertaking in some of the least explored areas of the planet.

“The trend is to go into deeper and deeper water in search of oil and gas,” says Hartmann.

“In these environments we can’t use divers so we need remotely operated equipment. This has to be operated by crew on diving support vessels. They operate subsea robots, which are like mini-submarines connected by a tether to the support vessel, and allow us to capture data.

“We do periodic inspection but also continuous repeat inspections to build up certain history of the degradation. Sometimes we do one-offs where there’s been something observed.”

Not only is it difficult to get equipment down to deepsea locations, an added layer of complexity is added by the type of plant down there.

“In deeper water, especially in the Arctic, thicker or more flexible materials are used for pipelines, for example,” says Hartmann.

“We can’t remove coatings so we use electro-magentic technology to look through.

“Also, flexible pipes are used to transport oil and gas in deeper water between floating platforms – but they have a lifetime. If the operator wants to extend this then he needs to justify that decision with an inspection of the risers.”

Advanced technology is used to carry out inspections of subsea equipment.

“The tools we use are small robots, they have a mechanism to move along a pipe, cameras to help control them and also for inspection,” says Hartmann.

Taking a boat packed with this hi-tech inspection equipment out to remote locations does not come cheap.

“One of these support vessels can cost up to £250,000 per day,” says Hartmann.

“The aim is to minimise the time the vessel is needed. Inspections must be fast but this partly depends on preparation.

“Pipes must be cleaned, so we install cleaning aids on the tool. The more information we can gather the better, so we use not only electromagnetic equipment but ultrasonics and other technology.”

Remotely operated vehicles (ROVs, also known as mini-submarines) are often used to take specialist tools from a diver support vessel on the surface to the plant.

Tools can include video cameras, sonars, manipulators, cutting arms, samplers and measuring devices among others.

Highly trained teams are required to manage the process and equipment, with oil companies spending up to £30 million per year on inspection contracts.

“Oil companies usually draw up inspection plans and contract specialised companies such as us through tender processes,” says Hartmann.

“An inspection contract can be worth anything from £30,000 to £2 million.”

Deploying the equipment – and the equipment that carries the equipment – is not an easy job in the kind of environments faced.

“To produce good inspections we have to overcome obstacles and adapt our methods,” says Hartmann.

“We have a lot of specialists on the support vessels: those using the ROVs; those servicing the vessel itself; and our two teams of two engineers, who work shifts.”

These are highly trained inspection technicians who monitor the tools and manipulate them when needed.

“You can’t go back to shore once you’re on site, so you need lots of equipment in case something breaks, [to ensure] you can fix it on the vessel.”

As engineering jobs go, being sent out to inspect or maintain subsea infrastructure is unusual, demanding and – for the right people – exciting.

“To maximise use of a vessel we need to have two shifts,” says Hartmann.

“Individuals work 12 hours on then 12 hours off and they can be offshore for four weeks before a crew change.”

Conditions are made as comfortable as possible given the remote and often harsh locations.

“There are high standards of living,” says Hartmann.

“There has to be as there is nothing else to do – we have modern rooms with a chef on board and entertainment.”

The frequency of inspections of pressured installations can vary from every six months to once a decade.

Caissons and structures are usually inspected visually and less frequently.

“We normally advise on the condition of the equipment and the need for repairs,” says Hartmann.

“We find all different sorts of degradation, such as where an anchor has fallen on a pipe for example or metal loss due to corrosion or cracking.

“Plant can also suffer from severe bacterial corrosion, sometimes on the underside where you would not see it from a visual inspection, even if you could get down to it.”

Husby says minimising inspections and maintenance work is the first priority.

“We try to avoid replacing equipment outside of planned times as it’s a huge cost. The cost of doing it on the sea bed compared to the surface is huge. Also, if you do this work as an emergency measure it is much more expensive again, and you risk bad weather delaying the work and causing the plant to be shut down.

“So you need systems that give confidence they will remain running.”

This is where the industry is looking for the future. “A vast range of technology is being developed at the moment,” says Husby.

“For example, we are involved in working on new valves that can be used in the oil well.

“The main challenge is getting confidence that these will work come what may. They are critical components of the operation and in deep sea conditions the operators need even more certainty about them.”

Any way of speeding up inspection and maintenance work is also highly sought.

“Vessels are expensive and if we can do work faster then it’s beneficial,” says Husby.

“We are looking for equipment that lets us replace subsea equipment quicker and also looking for lighter equipment to allow [us to use] smaller vessels.”

All this is high on oil & gas operators’ to-do lists.

“The challenge for oil producers at the moment is cost, as the price has come down dramatically and they are looking to cut costs at every point of the chain,” says Husby.

“Making subsea equipment more cost efficient is a key area for them.”