Norway’s Statoil is to keep its Snorre B platform shut in until an investigation finds the cause of a pit which formed at a subsea template.
The pit, described as “an abnormal erosion of mass under the template” was discovered on Saturday (17 May), and production shut on the template.
On Monday, Statoil shut in the entire Snorre B semisubmersible, production, drilling and quarters platform, after an attempt to restart the template, and 33 staff were removed to shore, after movement and hydrocarbon indications were observed in the pit.
Image: Snorre B, by Harald Pettersen, Statoil.
"The pit is stable and is being monitored continuously. The most important thing for us now is to clarify what caused the pit to form, and a number of explanations are being examined," says Bente Aleksandersen, Statoil's senior vice president for Operations South.
Snorre is in blocks 34/4 and 34/7 in the Tampen area of the Norwegian North Sea, northeast of Gullfaks and southeast of Knarr, in about 300m water depth.
Last night Statoil said: “Over the last 24 hours, no movement has been observed in the pit at the subsea template. The area is under continuous ROV surveillance and sediment samples have been taken. Brine (water with heavier sediments) was pumped into the well for a brief period in the event that there was some sort of connection between the pit and the well. There have been no signs of hydrocarbon leaks in any of the surveys carried out since the pit was discovered on 17 May. Statoil has decided to keep production shut down until the necessary investigations have been carried out.”
Snorre has been producing oil and gas since August 1992. It was discovered in 1979 and the Snorre A tension leg platform development approved in 1988. Snorre B was approved in 1998 and came on stream in 2001.
Production from Snorre is estimated at about 88,000 bbl/d in 2013. Last year Statoil started installing 250km of seismic streamers on the sea bed at the field for a permanent reservoir monitoring project. Operations to cover the cables was expected to start up again this summer and complete in 2015.
The Snorre field consists of several large fault blocks. The reservoir, at 2000-2700m deep, contains Lower Jurassic and Triassic sandstones of the Statfjord and Lunde formations. The reservoir has a complex structure with many alluvial channels and internal flow barriers.
Partners on Snorre are: Statoil 33.31%, Petoro 30%, ExxonMobil E&P Norway 11.58%, Idemitsu Petroleum Norge 9.60%, RWE Dea Norge 8.28%, Total E&P Norge 6.17%, and Core Energy AS 1.03%.