Neptune Energy said March 19 it saved about $12 million and cut emissions at the Duva development project in the Norwegian North Sea by using a vessel to install four enhanced horizontal subsea trees instead of a rig.

The installation marked a first for Neptune, the operator.

The subsea trees were installed using the Solstad Offshore-operated Far Samson vessel. The development, an oil and gas subsea tieback to the Gjøa semisubmersible facility, is located on production license 636.

“By introducing the latest available technology combined with quality planning and teamwork, we completed the installation safely, successfully and ahead of schedule,” Thor Løvoll, Neptune Energy’s director of drilling and well in Norway, said in a news release. “Deploying the subsea trees from a vessel saved about 20 days of rig time, reducing costs, time and emissions.”

The reduced rig time is equivalent to about $12 million in savings for project partners Neptune Energy (30%), Idemitsu Petroleum Norge (30%), PGNiG Upstream Norway (30%) and Sval Energi (10%).

By using a vessel instead of a rig, emissions were also cut by more than 60% during the installation activities. This is compared to direct emissions from operating a drilling rig with associated support vessels and helicopter transport, according to Neptune.

The subsea trees were deployed on the template wellheads over an 18-hour period. Total installation and subsea system testing were completed within eight days, Neptune said. Companies involved included TechnipFMC, Ross Offshore, Solstad Offshore, Oceaneering, Fugro, IKM and Tigmek.

The Odfjell Drilling-operated Deepsea Yantai drilling rig will drill and complete the remaining sections of the Duva well program during first- and second-quarter 2021, Neptune said.

First production from Duva is expected in third-quarter 2021.