The Transocean Leader rig has been chartered by Statoil to work on the northern flank of its Statfjord field in the North Sea.
Taken over from Amerada Hess on 6 January, the unit will drill and complete subsea wells to bring this part of the field into production on 1 August.
The charter, which runs to 20 August, has been required because of delays in receiving the Borgland Dolphin rig from Bideford Marine.
Owned by Norwegian shipping magnate Fred Olsen, this company signed a six-year charter with Statoil in the summer of 1997. Plans called for Bideford Dolphin to start work in the third quarter of 1998.
However, the owner now says that conversion work at Britain's Harland & Wolff yard in Belfast will not be completed until June.
Transocean Leader is the second rig Statoil has been compelled to hire for the project in place of the delayed unit. The first was West Alpha, taken over from BP Amoco on 21 December under a 130-day contract.
"To recover a bit of the delay, we've had to compensate with two rigs," explains Geir Tungesvik, reservoir utilisation manager for Statfjord satellites.
The rigs have been chartered in a tight market, he adds, and accordingly represent an expensive solution. The supply of units able to do both drilling and completion is limited.