Operators keen to grow production at existing offshore facilities often use tiebacks from nearby fields, and multilateral retrofits can make this possible when no slots are available.

Schlumberger carried out a subsea multilateral retrofit in the Barents Sea in 2021 and has since also carried out dry tree multilateral retrofits. 

At the same time, Schlumberger is working to modernize completions though all-electric intelligent completion systems, and the service company is combining the all-electric completion systems on a TAML 4/5 multilateral retrofit for a client. Schlumberger expects to execute multiple retrofit multilaterals paired with all-electric intelligent completions in 2023.


Multilateral Retrofits in Subsea Wells Accelerate Time to First Oil

Olav Lien, Schlumberger’s production systems manager for Scandinavia, said operators want their increased oil recovery efforts to generate high value at a low cost. Norwegian operator Vår Energi found new reserves close to the Goliat field and wanted to produce the resources, but there were no open slots in the subsea templates, he said.

Instead of investing in construction and installation of new subsea infrastructure, Vår Energi opted to retrofit an existing monobore well with a multilateral junction, which provided access to the new reserves while keeping existing production, Lien said.

The job, carried out from December 2020 to February 2021, represented Schlumberger’s first two subsea retrofit multilaterals and has resulted in additional orders from Vår Energi and new orders from Equinor, he said.

Another retrofit multilateral campaign for Goliat was in progress this summer, and a third is planned for the turn of the year, he said.

“Installing a multilateral in an existing producer and keeping that existing bore producing and adding another lateral to also produce from, that’s what’s quite unique about our technology,” Lien said.

Schlumberger multilaterals
Vår Energi used retrofit multilateral technology to target newly discovered accretive reserves utilizing Goliat’s existing infrastructure. (Source: Schlumberger)

The first step was to set the plug in the main bore to isolate and protect the existing reservoir to avoid damaging it. Next, the whipstock moved in and a hole was drilled to access the pocket of oil, and the well was completed, he said. The junction was then installed in steps, with one piece in the main bore and the other into the lateral.

“These two latch together to form a seal for well integrity,” Lien continued.

Once the plug was removed, it was possible to produce from both, he added.

Last year, Schlumberger deployed the all-electric Manara production and reservoir management system in Equinor’s Heidrun field. Schlumberger said the Manara system delivers in-situ measurements of pressure, temperature, flow rate and water cut all across the formation face and eliminates the uncertainty of zonal contribution. Sensors are packaged in a compact station with an electric flow control valve that has infinitely variable settings controlled from the surface through an electrical control line.

Manara was developed as an electric system because of the inherent limitations with hydraulics over distance, he said.

Plus, Lien said, “electric is superior versus hydraulic from a technology perspective.”

Heidrun’s Manara deployment consists of six modules deployed in five zones.

Olav Lien, Schlumberger
Olav Lien, Production Systems Manager - Schlumberger Scandinavia. (Source: Schlumberger)

Equinor “clearly saw that the system did everything that we said it was going to do, with measuring the water cut, the flow rate, the temperature in the zone,” Lien said. “They were able to manipulate production through the choke on the flow control valve. They were able to close zones which were producing water and were able to in the well actually manipulate to eliminate water we didn’t want to produce and to produce oil and gas.”

Since the Manara system installation for Equinor at Heidrun, Schlumberger has received additional orders for a similar system to be installed in late first-quarter 2023, he said.

“We’re gaining traction on both these technologies,” Lien said. “We’re also in dialogue with customers on combining them and installing Manara as lateral control in a multilateral installation.”

Looking toward the future, Lien said, it is interesting to think about how to modernize completions technology through electrification of the entire completion.

Schlumberger is working on one of the final pieces needed to offer a fully electric completion.

“An all-electric subsurface safety valve is the main building block we are currently missing,” Lien said, adding the technology Schlumberger is developing is expected to go to field trial in fourth-quarter 2023