Open water abandonment

Audrey Leon speaks with Helix Energy Solutions Group’s David Carr about a new system from the Subsea Services Alliance, which seeks to safely drive down the cost of well abandonment operations in open waters.

Helix Q5000 is designed to allow simultaneous deployment of an intervention riser system with the ROAM tool.

As the oil and gas industry settles into its “lower for longer” mindset, service companies are looking to help operators cut costs while continuing to ensure safe operations.

The Subsea Services Alliance (a collaboration between Helix and OneSubsea, now owned by Schlumberger) launched its Riserless Open-water Abandonment Module (ROAM) system in early October this year, with the aim of reducing both cost and risk in lower completion abandonment operations.

“One of the key drivers for developing this system was to find a way where we could extend our current riserless work in the North Sea, and take that a step further to be able to pull tubing in open water,” says David Carr, vice president – Commercial, Helix. “We wanted something light enough that could go onto the older wells in the UK, but also could work at the pressures and depths down to 3000m that we find in the Gulf of Mexico,” Carr says.

“Going forward, as we developed it and we discussed it with other operators, there was and remains a lot of interest to use the system to get away from the traditional cut and pull methodology of abandoning wells.”

Render of the riserless open-water abandonment module (ROAM). Images from Subsea Services Alliance.

Carr says in traditional operations, Helix will take a riserless or riser-based vessel to do a lower abandonment, where plugs are set at the bottom of the well, essentially killing the well, and then cutting the tubing. “The operator then needs a rig to come onto the well to cut and pull all the casing strings out,” he says.

Using the ROAM system could ultimately remove the need to bring a drilling rig onto the well for abandonment, he adds, thereby reducing cost. The 18.75in large bore system, the Subsea Services Alliance members say, will enhance well abandonment capacity from a well intervention vessel by allowing tubing to be pulled in open water in a safe and environmentally contained manner.

While open-water tubing pulling is currently allowed in the US Gulf of Mexico and Helix’s own vessels – Q4000 and Q5000 – can perform this operation already, not all operators are comfortable with the process just yet, Carr says.

But, the ROAM system seeks to address potential concerns. “We developed this system with the mitigation of the potential for environmental leaks in mind,” he says. “The ROAM system gives us the ability to unseat the tubing hanger, wash behind it, and get rid of possible pollutants, before pulling the tubing out.”

A 2D render of the ROAM system.

How does it work? Carr describes the process as follows: “First, we will go on with Helix’s standard riserless or riser-based intervention system; we kill the well and run wireline or coiled tubing to install barriers, circulate out the completion fluid, place the cement and cut the tubing; once we have done that, the well is effectively suspended. We are then able to remove our intervention riser package off the well, as we simultaneously lower the ROAM system down on a crane and put it on the well.

“What we then have in place is a full 18.75in bore access to the well. We have two shear-seal BOPs (blowout preventers) in the well and an annular BOP at the top. Once the ROAM system is installed, we are able to run in with a tubing hangar release tool, run in on drill pipe. We latch that into the tubing hanger, shut the annular, and then unseat the tubing hanger.”

Carr says that had the operation been done without the ROAM system in place, and had there been any contaminated fluid, it is at that point the fluid would get released into the ocean. “But, by having the annular closed, we are able to circulate all of that fluid to surface before we open the annular again and start pulling the tubing open-water,” Carr adds.

The ROAM system, which is the second system built by the Subsea Services Alliance, will be engineered and built at the OneSubsea manufacturing facility in Aberdeen, according to a statement by the alliance in October. The system, which will complement existing intervention riser systems and subsea intervention lubricators, is expected to be available in Q3 2017.