Operator-backed plasma milling to make North Sea debut in 2017

A revolutionary technology by GA drilling can cut the time required for section milling from 12 days to several hours and is to undergo full-scale onshore testing next year at Weatherford’s Houston facility.

Image credit: GA Drilling

The Plasmabit method uses a device similar to a welder’s arc to generate extremely high temperatures to melt a section of casing string at the point where a cement barrier has to be placed during a Plugging and Abandonment (P&A) operation.

Onshore testing in the US next year will be partially funded by ConocoPhillips, Statoil and BP and this will be followed by operational deployment in 2017 in North Sea fields owned by ConocoPhillips, Tomas Kristofic, Chief Technology Officer of GA Drilling, said.

ConocoPhillips’ plans a series of North Sea P&A campaigns at an estimated total cost of around $3.5 billion.

The operator is trying to reduce the costs by gaining technological advantages, Tim Croucher, the company’s Norway Decommissioning Manager, told Decom World.

“The opportunity that increase in work is creating in terms of developing new technology and new methodology, new materials, whatever it might be, has the potential to give you both a significant decrease in decommissioning costs but also give you the long term containment assurance that we need to deliver,” Croucher said.

Weatherford is helping to provide the physical resources required to bring the system to market. GA has only 75 employees, and lacks the means to set up the testing rigs necessary to run large-scale iterative testing programs.

The Plasmabit method was originally developed by four former students of the S lovak University of Technology in Bratislava, who went on to found GA Drilling.

One of these students was Tomas Kristofic, who is now Chief Technology Officer at the firm.

Kristofic said the electrical plasma has a number of advantages over traditional milling, which uses a rotating cutter to scrape away the metal lining of the wellbore.

Shaving time

 “The conventional approach is that if you have to remove the wellhead string, you have to pull up the whole of the production and completion strings, then you need the rig or light well-intervention vessel to do the milling and this takes from 10 to 12 days. Our method will take from several hours to two days at the most. It’s a complete structural change,” Kristofic told Decom World.

The GA drilling system has no moving parts. The arc rotates using hydrodynamic and magnetic forces but the probe remains stationary, which means that it can anchor itself in the bore. It then relies on a suit of sensors that supplies real time information to the computers that control the operation.

Rather than grinding away a long tube of high quality steel over a number of days, the high intensity process melts the steel in a number of hours.

An additional advantage is that the steel casing is disintegrated rather than cut into 5cm chips of swarf (shavings), which makes it easier to remove debris from the wellbore.

Early adopters

GA Drilling has been working on Plasmabit for over three years and during that time is has relied on a mix of research funding.

The European Union’s Framework fund for research and technological development has supplied Eur12 million ($13.6 million), and a Joint Industry Program made up of oil operators has covered around 10% of development costs. Other funding is coming from Weatherford and from GA Drilling itself.

The firm is now in talks with Weatherford to finalise the concept for phase four of the research, which will run for the next 18 months, and which will be undertaken with operator partners ConocoPhillips, Statoil and BP.

The first field testing will be carried out by ConocoPhillips, which began talks with GA Drilling in October last year and agreed a partnership deal in January.

The below graph on expected Cessation of Production declarations is taken from Decom World's North Sea Decommissioning Strategy Report 2015 and uses data from the UK government's energy department.

Emerging technology

Norway’s Statoil is another operator with a large-scale North Sea decommissioning program under way.

Steinar Strom, the company’s leading advisor on P&A, believes plasma milling is promising, but said there is still a long way to go before it can be regarded as proven in field conditions.

“It’s not mature enough to take it really seriously yet, but we see great potential in the technology. It may be true that they can cut the time needed to mill to several hours, but you still need to put in the cement,” Strom said.

“We’re following the developments with Weatherford closely. It’s not often that you see a smaller company team up with such a big beast,” he said.

Statoil is pursuing a parallel research project into thermite-based melting that may be able to achieve similar results, Strom said.

This method is at least two years away from operational deployment, he said.