RWLI makes its mark

April 1, 2015

Ask about subsea well intervention and most assume it’s riserless light well intervention you want to talk about – for good reason. Elaine Maslin reports.

Subsea light well intervention visualized by FMC Technologies. 

Riserless light well intervention is a growing area, seen as able to reduce well intervention costs, by bypassing the need to use a drilling rig, and increasing the number of well interventions that can be performed. While once a method operators were nervous to use, it’s now well-established in the North Sea and gaining acceptance in the Gulf of Mexico.

Contractors and service providers are joining forces, eying new areas to introduce their technologies and operators are pushing the boundaries of RLWI into deeper waters.

Why riserless?

Riserless light well interventions are performed to address well integrity issues and maintain or enhance well production without using a riser, by deploying intervention tools into the well on wireline, electric-line and slickline using a subsea intervention lubricator. A range of activities can be performed, from acquiring production data and running integrity logs to retrofitting gas lift valves and performing scale squeezes. Riserless stimulation, or high-rate pumping for fracturing, is also being used to improve production.

“Over a period of time, reservoir conditions change, such as producing more water or you might want to set plugs to re-perforate,” says John Thomson, intervention engineer, Global Wells Organization, BP, based in Aberdeen.

For subsea wells, the need for interventions is greater and will become more so as wells become more significant-sized producers in deeper water. Subsea wells, which, due to fewer planned interventions typically have a much lower recovery factor than dry tree wells, actually require even more attention, says Henning Berg, President, Subsea Services, OneSubsea.

Using RLWI, operators can reduce vessel costs and perform more interventions. You can operate on 20-30 wells a year using RLWI, says Bjarne Neumann, director of well intervention services at FMC Technologies, compared to 10-15 per year using riser-based operations.

Furthermore, money spent on intervention brings greater return than cash spent on greenfield projects, says Carl Roemmele, Well Access Lead at GE Oil & Gas. “This is why we are seeing the big drive into monohull deployment,” he says. “Monohulls are a quarter to a third of the cost of a drill rig, depending on what you get on it and the water depth. If you can go behind a rig to tidy up wells, do testing or pick up intervention, you can save rig days and money. Most reports you read predict double-digit compound annual growth rate in the intervention space over the next 3-5 years.”

Dominating the market

To date, Norway and the UK North Sea have been a front runner in RLWI, due to the fact it has the most mature subsea trees in the world, Neumann says, with dedicated riserless light well intervention vessels established in both basins. “Operators are now so familiar with RLWI they even have a vision all intervention will be done riserless in the future. That is their target because it is more cost effective. It is a technology proven over the years to be reliable, safer and more efficient,” he says.

BP has had a dedicated well intervention campaign west of Shetland on the UK Continental Shelf, under a long term alliance led by Island Offshore (with Oceaneering, FMC Technologies and Altus Intervention) using the Island Constructor, since 2009, as well as operations on its other North Sea assets with Helix Energy Solutions, using the Seawell, Well Enhancer and Skandi Constructor. The firm has 197 subsea wells on the UKCS, the deepest in about 500m water depth, west of Shetland, where the weather window spans just April to mid-September.


Helix Energy Solutions’ Q7000 semisubmersible well intervention vessel.
Image from Helix Energy Solutions. 

John Thomson, intervention engineer, Global Wells Organization, BP, based in Aberdeen, says the long-term contracts have meant continuous improvements have been made, both around managing the challenging weather conditions west of Shetland [OE: January 2015] and operationally. In 2007, BP performed one subsea well intervention operation in the North Sea a year. It is now about 12, in that short season, says Thomson, and they’re delivered on time and on budget. “The North Sea is not a challenge any more [for RWLI], it is becoming routine” he says.

Colin Buchan, Wells Engineering Manager Subsea Well Intervention at Shell, says Shell first used RWLI in the North Sea in 1994. Since then the technology has been used more and more in the North Sea and now in the deepwater basins in the US Gulf of Mexico, Brazil and West Africa. However, to be fully adopted in deepwater, technology, vessel capabilities and economic viability need to be addressed.

Deepwater opportunities

“Shell has a long history of using RWLI techniques,” says Buchan, co-chair of this year’s Deepwater Intervention Forum conference, organized by OE and held in Galveston. “In up to about 1000ft water depth, it is established technology. Beyond 1000ft, there are some technology concerns within the operator community as to reliability and environmental protection.”

Some of the concerns are around the ability to isolate the well from the surrounding environment on the seabed. “It is a dynamic seal which you are running a conduit wireline or slickline through and that has to isolate the well fluids from the environment,” Buchan says.

Using a riser-based intervention system, the seal is on the rig floor. On the seabed, the seal has to be able to deal with the hydrostatic pressure. The scenario when the hydrostatic pressure is greater than the well pressure creates additional demands on the sealing mechanism, which means proving a reliable pressure control system is crucial.

It’s an area Shell is working on closely, alongside technology vendors. Shell is keen to have the technology ready to work on its subsea well stock, which includes deepwater wells offshore Nigeria, Brazil and in the Gulf of Mexico. So far it has performed subsea well intervention operations on wells at 3800ft off Nigeria and to 6200ft off Brazil. The current industry record is 8100ft, Buchan says.

“We are going through a learning curve as an industry on how to maintain an effective seal in these water depths. It is coming, slowly,” Buchan says.

An emergency disconnect package and lower riser package. Image from OneSubsea.

Offshore Nigeria, Shell developed a system which could be mobilized on a vessel of opportunity. Instead of using a conventional rig, with an integrated subsea lubricator system, the firm used a lower riser package, emergency disconnect package and a pressure control head – effectively a workover riser system adapted to be a subsea lubricator system. The same system, owned by Shell, can also be used from a conventional rig and was recently used in this way, this time with a riser, due to the need to used coiled tubing.

It is a market that is expected to grow. “Deepwater is an area a lot of people speak about as a potential area for growth and I believe that’s the case as well,” Buchan says. “There will be more opportunities as we meet the technology challenges and demonstrate the capability. But this needs to be built on firm foundations and we need to make sure as an industry we are doing it correctly and doing it right, the first time, every time.

Coiled tubing

There is also an aim to be able to provide riserless coiled tubing interventions. Although sand removal can be performed using riserless systems, some wells, may require sand removal using coiled tubing and coiled tubing is currently unable to be run through riserless systems.

BP has this issue in some UK North Sea wells, for which it is looking for a solution. “We would like to use riserless coiled tubing but, while it has been talked about for a good few years, the capability has not been developed yet,” Thomson says.

Island Offshore, working with Baker Hughes, last year used open water coil tubing drilling from the Island Performer on the Rogfast road tunnel connection project outside Stavanger. The pair drilled in the Boknafjord using coiled tubing without a riser from the monohull Island Performer to collect rock samples from the seabed for the civils contractor.

But, it is still early days for riserless coiled tubing, many believe. “A number of service providers are looking into doing open water coiled tubing in a safe manner,” Neumann says. But, it might not be that easy, he says, because established codes would be challenged is when the tubing effectively becomes the riser. “I don’t see open water riserless coiled tubing being operated in the next two years,” he says.

Helix Energy Solutions’ operates the Skandi Constructor.Image from Helix Energy Solutions. 

Global growth opportunities

Even without expanding the RWLI envelope, operators, vendors and service providers see a growing RWLI market. Regions outside the Gulf of Mexico and North Sea are showing increasing interest in RWLI, but their take up could be hindered by the availability of equipment and/or the operators have yet to use the technology and are a bit reluctant to be the first in their region, Neumann says.

“The industry has developed a wide variety of downhole tools and has increased the range and scope of what can be accomplished using riserless systems. The challenge is to ensure that operators are fully aware of these recently developed capabilities. There are also the wells which have sand ingress, which require coiled tubing operations.

There’s also a “chicken and egg” scenario. Service operators will be unwilling to move their vessels into regions, such as West Africa or Brazil, if there’s not enough work there for them. Island Offshore, for example, has capability to go to 1500m, but it would need a campaign to make it viable to move a vessel to say West Africa. In such circumstances, operators need to work together to spread the cost of a vessel, Thomson says.

However, “As a standalone business, well intervention is at an early stage,” says Scotty Sparks, Vice President, Commercial/Strategy, Helix Energy Solutions. “Riserless intervention is quite well-established in the North Sea, and both riserless and riser-based intervention from a dedicated vessel is common in the Gulf of Mexico, but in other regions, well intervention is still predominantly performed from a rig at a much greater cost. If you consider the subsea tree count, however, Brazil and Africa are the high points and we see a strong business case for both riserless and riser-based operations in those areas.”

FTO Services’ Island Performer. Photo from Tor Aas-Haug/Mediafoto.

Integrated service offerings

Service companies have been working hard to offer attractive packages. FTO Services, an RLWI partnership between FMC Technologies and ship owner/operator Edison Chouest Offshore, recently relocated the upgraded RLWI vessel Island Performer, operated by Island Offshore to the Gulf of Mexico. [See more on the Island Performer on page 26.]

Last year, Helix Energy Solutions, OneSubsea, and Schlumberger formed an alliance to focus on subsea well intervention, leveraging Helix’s growing dedicated intervention vessel fleet with OneSubsea’s equipment and technologies and Schlumberger’s downhole expertise. The alliance was officially signed on 6 January 2015.

“Our thinking was to create a full package and to cover the full value chain. You need the vessel, the access package and the in well services. Having the full package minimizes the interfaces and number of contract points with the client, as well as creating possibilities to optimize the crew size and the equipment,” says Henning Berg, OneSubsea. “Helix is the leader in intervention vessels, OneSubsea has been making intervention packages for the last 20 years and Schlumberger is the best in class for in-well services.”

Helix currently has five well intervention vessels, from small intervention vessels up to a heavy duty semisubmersible, and it is expanding its fleet. This year it will take delivery of the Q5000 semisubmersible, next year two large monohull units will be delivered to work for Petrobras, and in 2017, the Q7000 semisubmersible will be delivered. Intervention packages are due to be replaced on some of the older vessels, Sparks says.

The alliance sees growth opportunities, in Brazil, Africa and Asia Pacific, where it can draw on the established bases of its component companies, Sparks says.

FMC’s Neumann sees similar opportunities to make efficiencies, with integrated and earlier contractor engagement. “At the moment you build a vessel, build a stack, and then some time down the road the vessel and stack owners and others meet, often too late to make changes,” he says. “To be partners in the planning process would enable us to collaborate to ensure that the vessel is designed with RLWI in mind so that it can be operated more efficiently.”

“We can reduce the amount of maintenance, reduce the number of power lines, and I believe one day we will see the industry move forward various packages being deployed from one vessel, for activities such as maintenance. So you have one maintenance team, and not three, and this will bring the economics down,” Sparks says.

GE Oil & Gas is also beginning to flex its muscle in this area. The business recently reorganized four related business units, including new build work over, intervention and completion equipment, offshore operations, a new productions introduction team (research and development) and the Wellstream subsea construction group into a single entity – Well Access.

Roemmele says GE Oil & Gas wants to offer something different, leveraging its business streams, products (the “GE Store”) and capabilities as well as through forming strategic partnerships, often on a project to project basis to address particular issues for clients. An example of technology GE is developing which could then be used in the well intervention space is the 20,000 psi blow out preventer project it is involved in. “We have the technology in the valves space that we could put to use from an intervention technology point of view,” he says. GE Oil & Gas is also working to make components lighter, to reduce weight and footprint, he says. Sensing and prognostic capabilities used in other sectors, such as aerospace, will also come into the picture he says, to enable better intervention planning, which could be particularly useful for more remote installations.

The opportunities

The opportunities seem abundant, the technologies ready and continuously being extended and the contractors and service providers primed to meet operator’s needs. “We have an increasing number of subsea trees around the world and in order to maintain production, operators need to do more intervention,” Neumann says.

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