Use of Solstad Offshore’s Far Samson vessel, instead of a drilling rig, for the four Enhanced Horizontal Subsea Tree Systems (EHXTs), brought multiple benefits.
Neptune’s Director of Drilling & Wells in Norway, Thor Løvoll, said: “We completed the installation safely, successfully, and ahead of schedule.”
Deploying the subsea trees from a vessel, the company calculated, saved about 20 days of rig time (and consequent savings of close to $12 million for the license partners), with 60% lower emissions compared with use of a rig.
The EHXTs were installed on the template wellheads over an 18-hour period, with all installation/subsea system testing completed within eight days.
Other companies involved in the operation were TechnipFMC, Ross Offshore, Oceaneering, Fugro, IKM, and Tigmek.
Duva, in production license 636, is an oil and gas subsea tieback to the Gjøa semisubmersible platform, which Neptune Energy also operates.
Neptune’s Head of Gjøa Subsea Development, Crawford Brown, added: “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.”
The semisubmersible drilling rig Deepsea Yantai, operated by Odfjell Drilling, will drill and complete the remaining sections of the Duva wells during 2Q/3Q.
Duva is 14 km (8.7 mi) northeast of the Gjøa field in a water depth of 360 m (1,181 ft). First production is due to flow in 3Q.
Other partners in the license are Idemitsu Petroleum Norge, PGNiG Upstream Norway, and Sval Energi.