Oil rigs have been integral to the offshore energy industry for decades, but things may be about to change thanks to ABB’s project to relocate all necessary equipment straight to the seabed.
This new automated method of production has the potential to save oil and gas companies hundreds of millions of dollars in expenditure, with Statoil predicting CAPEX savings of $500m for one of its projects. The technology is also intended to extend the life of existing assets.
One of the biggest R&D projects in ABB’s history began when the company was approached by Statoil to see if there was a way to provide enough power to the seabed to run a factory. A contract was signed in 2012 for the $100m development, launching what is now known as the Subsea Power Joint Industry Program (JIP), which is due for delivery in 2020.
Chevron and Total are also involved in the development process, which has attracted serious interest from other major operators in the offshore industry.
“It’s very important for companies – that’s why they’re pouring money into this,” says Dr Jan Bugge, ABB vice-president of subsea technology and project director of the ABB-Statoil Subsea Power JIP. “They do it to get more out of the ground because if you put the equipment on the seabed, you can produce much more efficiently. Power consumption goes down and you’re also closer to the wells.”
The technology has been designed with deepwater production in mind for sites that are further from the shore in remote locations such as the Arctic, opening up new possibilities for exploration with greater recovery rates and reduced operational costs.
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By GlobalData“You can also go much deeper,” says Bugge. “We designed this system for 3,000m so that we can sit it in Brazil, for example, or the Gulf of Mexico, or Asia.
“We can do distances up to 600km from the shore, so that we can reach virtually all the known assets and we can transfer up to 100MW of power – which is a lot. It’s a medium-size city that we could supply.”
Dr Kai Hansen, project manager of ABB’s Subsea Technology Program, adds: “From a user perspective, there should be little difference between running a subsea factory as a topside factory.”
Pressure-compensated design
At ABB’s subsea lab in Oslo, individual modules are developed through a pressure-compensated design process, which sometimes literally pushes components to breaking point. This ensures that any weaknesses are identified in the development phase and rectified before deployment.
“There are two principal philosophies we could have chosen,” explains ABB R&D programme manager Dr John Pretlove. “One is that you use pretty much off-the-shelf, existing technology today. You put it in a container that will withstand the pressure of the seawater, but inside the tank it’s atmospheric pressure. It would be like a submarine.
“The alternative, which is the solution that ABB has gone for, is to flood that container with oil so that you can maintain the electrical integrity, and you can now have a much thinner wall, because there’s not the pressure difference from the seawater on the outside to the oil on the inside. So you can make a much more elegant solution, but you haven’t moved the problem.
“With the first philosophy, all of the interconnects, any kind of signal or power which goes from inside the tank to outside the tank, will see a very large pressure difference. So it can represent a weakness.
“With the alternative approach where you fill it with oil, you don’t have that problem because the pressure on the inside is pretty much the same as the pressure on the outside. But you’ve moved the problem, because now all the components on the inside need to tolerate that pressure.”
The thinking behind having a slightly longer development process is that it will result in minimal maintenance during operations. The equipment is more likely to be capable of withstanding the extreme conditions encountered in subsea environments and has been designed to last for the duration of a well’s life, an average of 30 years.
Subsea lab and pressure tests
ABB’s subsea lab is in operation 24/7, 365 days a year and largely automated, meaning that testing can continue around the clock without any interruptions.
If materials used for modules fail to meet the rigorous demands during testing, ABB goes back to the supply chain to source a more robust alternative. This process continues until ABB is satisfied that the modules are capable of meeting the necessary operational requirements, with every variable taken into consideration during development.
“We go down to the various components, tailor-make those components so that they are the right ones for that application and then make modules, and then make products,” explains Bugge. “So, we build it very much from scratch, understanding the physics, understanding the challenges that they have at deep pressure.
“Making products and making modules that are fit for this purpose; that’s quite important, that distinction. That’s why this is a fairly long project, because we really need to understand physics, how this all works, so that we make products that are able to handle this.
“The modularity is very important and that you can make standard products that can fit a number of applications. The industry wouldn’t be able to handle that you do a certain development for every field. So they are standard, modular components and products that can handle the various environments.”
The industry term ‘technology readiness level’ is a grading system for how mature a technology is. The subsea power solution is currently at TRL3 and will become TRL4 before the end of 2019, shortly before it is deployed and reaches TRL5, meaning it is mature enough for industrial operations.
All equipment developed by ABB in the project conforms to IEC, IEEE and API industrial standards.
In addition to the tiny modules in the lab, ABB has been putting much larger units through qualification tests inside a 5,000l pressure vessel simulating water depth of 3,000m at pressures of 350bar.
Shallow water tests have also been performed on a 50t drive unit intended for the seabed, in Vaasa, Finland. These shallow water tests are largely for the thermal aspect of the equipment, intended to confirm tolerance for both extreme heat and pressure.
“We are simulating high-pressure by putting the equipment into pressure vessels,” says Dr Bugge.
“We have 19 of these pressure vessels at various locations in Europe and there we test that aspect of deepwater or high-pressure.”
Slashing the carbon footprint of oil production
Oil and gas production is not typically known for its low emissions, yet ABB’s subsea technology could substantially reduce a development’s carbon footprint in the process.
There won’t be any need for sites to be manned, as everything will be controlled remotely. There also won’t be any ships going back and forth from the site because extracted oil and gas is sent to the shore via a pipeline, reducing disruption to marine life.
“You can take the power directly from shore rather than generate that power at 30% efficiency with the gas turbines offshore … and it can be clean energy that you’re taking,” says Bugge. “So it’s less polluting just from that aspect, but it’s also that there are no helicopters going back and forth, there is no spill from topside stuff, it’s really designed to handle that, so it will be better.”
ABB’s data monitoring systems on the assets will alert operators if any maintenance is required.
Previously, each piece of equipment would need its own power cable. With ABB’s subsea technology, just one power cable is sufficient for the subsea entire factory.
The other advantage of having everything operate on the seabed is the temperature. The hotter equipment becomes, the more its efficiency decreases. The cold subsea environment helps keep components cooler and allows them to run closer to their optimal level.
“The lower the temperature is inside the equipment, the better the equipment can handle it,” adds Bugge. “It’s like your mobile phone; if you leave it in the sun, it’s not really good for it in the long run. So basically, you eat lifetime by temperature. You need to have as low a temperature as possible. You want to put equipment down there that can last for up to 30 years.
“It’s very different from things that you have on the platform, [which] you might want to service every year. Here, you want to minimise the service. You can’t just send a service engineer down there.”
