Electrifying

The all-electric subsea Xmas tree, complete with electric downhole safety valve, has finally made its debut. Elaine Maslin spoke to Total’s Frederic Garnaud about the achievement.

The K5F-3 subsea all-electric Xmas tree from OneSubsea. Photo from Total E&P NL.

This summer, a shallow water subsea well in the Dutch sector of the North Sea was brought online. While this might not sound significant, it is noteworthy due to the technology proved on the well.

The K5F-3 well has demonstrated the all-electric subsea concept, including a downhole safety valve (DHSV). Two earlier wells on K5F had all-electric trees – also firsts – but a hydraulic DHSV. Furthermore, the components involved have been qualified to 3000m water depth, making it a deepwater-ready technology.

The system uses Schlumberger-owned OneSubsea’s latest generation CameronDC subsea Xmas tree and controls technology and a Halliburton electric downhole safety valve (eDHSV).

It’s an achievement, towards reducing cost, simplifying the subsea system and enabling ultra-deepwater and long step outs, says Frederic Garnaud, deep offshore research and development program manager at French oil major Total.Once the technology has been observed working smoothly for a few months, subsea all-electric will become the base case for subsea control environments for Total deepwater developments, from 2017 forward, Garnaud says.

“The main benefit of electric control is in the cost reduction because the current technology for subsea control is based on hydraulic control, which requires a network of umbilicals, with electric cables and hydraulic and chemical lines,” he says. “These systems are expensive, very complex, and difficult to install. There is a major cost saving through simplification or removal of the umbilical.

“Electric technology will also be an enabler for frontier developments in deepwater. The industry is beginning to pay some attention to water depths of 3000-4000m. There’s no doubt, in such water depths, electrical control will be much easier to implement. It will really be an enabling technology. If you consider also long tiebacks, over 200km, there’s no doubt as well that electric control will enable those developments.”

By using all-electric, and eliminating hydraulics for power and signals, control-system commands can be sent in rapid succession, with high-speed communication also providing near-instantaneous communication with equipment – such as the status of the electric DHSV – as well as feedback on subsea conditions. Going all-electric also eliminates the potential for hydraulic leaks and the issue of hydraulic-fluid disposal.

Proving up an all-electric subsea tree became a goal for Total in the mid-2000s. It chose the K5F field in the Netherlands as its test bed, using the all-electric CameronDC technology, which Cameron as it was had been working on since 1999, for the gas development’s two subsea wells.

The K6 platform. Photo from Dufour Marco/Total.

A hydraulic DHSV was selected for the project because the eDHSV was not yet fully qualified and available for use at the time, Garnaud says. The two-well project, on a three-well template, was tied into the K6 platform, then on to the K6-P/L platform, about 20km away.

The system has largely proved itself, with 100% actuator reliability, but there were some glitches around the subsea control modules and the hydraulics system, according to Total.

The latter only served to encourage the completion of development of an eDHSV with Halliburton. The second phase on K5F, the planned K5F-3 well, kicked off in 2013, with ongoing work on the eDHSV. Halliburton’s eDHSV uses electric linear actuators, adapted from its DepthStar DHSV. The subsea control modules were also upgraded, compared to what was on K5F.

The full system, tree and eDHSV, were fully assembled at OneSubsea’s facility in Germany late 2015 and put through system integration testing before being shipped out for installation this year. The well was completed in mid-June, followed by perforation and then first production in early August.

“What we are doing in the Netherlands is a demonstration of subsea control technology for future assets in the deep offshore environment,” Garnaud says. “All of the components on this well are qualified for 3000m of water, so the eDHSV can run in the Gulf of Mexico or the Gulf of Guinea in deepwater. “Each component of the Xmas tree is also qualified for 3000m water, so we can use it on deepwater applications as well,” he says. Total has also been working on other building blocks for deep offshore developments, including subsea chemical storage. “With this we can completely remove the subsea umbilical,” Garnaud says. “Just install electric power cables with fiber optic for control and that’s it. By installing subsea electric control and subsea chemical storage you can save around 20% of the capex for facilities on the subsea satellite.”

Another Total project, called SPRINGS (Subsea PRocess and INjection Gear for Seawater), is working on a subsea seawater injection system, which would enable removal of the need for water injection flowlines from the topside facilities. This would “save a massive amount of money,” Garnaud says. It’s about simplicity, “simplifying the SURF (subsea umbilicals, flowlines and risers) package,” he says. And it’s also about subsea technology cost reduction, which has been a strong focus for Total since before 2014.

But, it’s still early days and that’s largely due to needing more suppliers that are able to offer this equipment – and compete on tenders. “What is not really available today is the full range of demonstrators for valve control, actuators, the various pressure wrenches for the valves,” Garnaud says. “What’s also missing for real projects is competition among the technology providers. All of the major subsea suppliers, FMC Technologies, GE Oil & Gas, etc., are working on the subject but none of them has a full range of equipment today. What’s important for us from now on is to promote competition in the technology so that, from 2017 on, we are able to launch tenders for full electric control of subsea assets.”

While within Total there is an understanding of the benefits of this technology for deep offshore projects, the challenge will be persuading partners to embrace it as well. Even so, there’s a strong trend towards all-electric across the industry, Garnaud says, following on from moves already made by the likes of the aeronautical industry – Concorde had first electric controls partially replacing hydraulics back in 1969, he says. In fact, the linear actuators on the eDHSV have been derived from aerospace, he says.

“Today, there’s no question about electric control as being tomorrow’s subsea control technology,” Garnaud says.