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Neptune installs enhanced horizontal subsea trees without use of drilling rig

Neptune Energy announced the safe and successful installation of four enhanced horizontal subsea tree systems (EHXT) for the Duva development project in the Norwegian sector of the North Sea. The installation was carried out by a vessel instead of a rig, reducing installation time, costs and operational emissions.

The Duva development, on Production License 636, is an oil and gas subsea tieback to the Gjøa semisubmersible facility. Neptune Energy is the operator of both the Duva project and the Gjøa facility.

A video of the operation can be viewed here.

While conventional installation of EHXTs would be carried out with a drilling rig, Neptune, together with its partners and contractors, conducted the installation using the vessel Far Samson, operated by Solstad Offshore.

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

The 20 days of reduced rig time is equivalent to approximately $12 million savings for the license partners. By using a vessel instead of a rig, emissions were reduced by more than 60% during the installation activities. Calculations based on direct emissions from operating a drilling rig with associated support vessels and helicopter transport versus the use of one vessel.

It was the first time Neptune Energy has installed EHXTs in a standalone operation with a vessel. They were successfully deployed on the template wellheads over an 18-hour period, with the total installation and subsea system testing completed within eight days. The operation was carried out in close cooperation with TechnipFMC, Ross Offshore, Solstad Offshore, Oceaneering, Fugro, IKM and Tigmek.

Neptune Energy’s Head of Gjøa Subsea Development, Crawford Brown, added: “We are progressing with the Duva project at pace and have reached an important milestone. The efficient installation of the subsea trees allows the project more schedule flexibility as we enter the drilling and completion campaign for the Duva production wells. Duva is an important part of Neptune’s geographically-diverse, gas weighted portfolio of developments, and will both increase production and extend the operational life of our operated Gjøa platform.”

The drilling rig Deepsea Yantai, operated by Odfjell Drilling, will drill and complete the remaining sections of the Duva well program during Q2/Q3 2021.

The Duva oil and gas field was Neptune’s first discovery in the Norwegian North Sea, a strategically important area supporting the company’s growth. It is located 14 km northeast of the Neptune-operated Gjøa field, at a water depth of 360 m. Gross 2P reserves are 88 mmboe (gas 76%).

First production from Duva is expected in Q3 2021.

License partners on Duva, PL 636, are Neptune Energy (operator and 30%), Idemitsu Petroleum Norge(30%), PGNiG Upstream Norway (30%) and Sval Energi (10%).

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