Norske Shell AS used the Ocean Vanguard semisubmersible, operated by Diamond Offshore Drilling Inc. (DODI), to work in Draugen oil field, on Haltenbanken, in the Norwegian North Sea (northeast of Njord and Ormen Lange fields).
According to Norske Shell’s Callum Smyth, the company needed to do major servicing on some of the older wells. He said the drilling crews showed character despite the problems encountered in the field and that the work was done efficiently. Because of the crews’ adaptability, “with all parties pitching in to make the job both safe and successful…the Vanguard has now proven itself as a completions rig.”
‘Excellent teamwork’
Before the rig came to Shell in summer 2006, the Diamond Offshore crew had never performed completion operations with the unit. According to Shell, all companies involved—Diamond Offshore, FMC, Kværner, Vestbase, Halliburton, Schlumberger, Seadrill, Oceaneering, Expro, Odfjell, Fugro, Smith Red Baron, and Shell—managed to go straight into a subsea flow base replacement operation.
The operation was performed safely and within budget with difficult rig limitations. For instance, the work required custom-built skids to move the christmas tree and flow base on the rig.
SWIT
The Ocean Vanguard reequipped from drilling to seabed-based water injection and treatment (SWIT) work and conducted a two-well workover operation. DODI crews pulled the christmas trees and tubing, replaced tubing with new pipe, and refurbished the trees. The teamwork resulted in an impressive performance, according to Shell, and the operation planned for 73 days was delivered in 60 days.
One notable success was the fact that one of the trees pulled was turned around, with FMC working night and day for 4 weeks, and rerun as part of the project. This was not in the original work scope at the time of project sanction, says Shell, and the successful completion by the Ocean Vanguard crew prevented a second intervention with another vessel or rig.
The offshore crews have worked well together, illustrated by the results (three wells back in service) as well as the quality and quantity of the daily safety focus (STOP, TOFS, JSA’s, etc.).
Result
The Ocean Vanguard rig worked with Norske Shell for 98 days in 2006. The resulting four wells returned to service, contributing about 3,000 cu m oil equivalent, which is 20% of the Draugen total daily production.
The E1 well is online and producing 500-750 cu m/day oil, ready for gas lift. The SWIT wells are both running with a total of 21,000 cu m/day combined injection (maximum rate from pump) with a reduced back pressure (20 bar lower due to the larger tubing) and full integrity on the annulus and tubing.
Source
Rigamarole, Spring 2007, Diamond Offshore Drilling Inc., p. 47, www.diamondoffshore.com/downloads/rigamarole_spring_2007.pdf