Ekofisk Bravo

Rig:

Ekofisk Bravo Platform

Date:

22 April 1977

Location:

Ekofisk Field, Norwegian Continental Shelf

Operator:

Phillips Petroleum Company

Introduction

The Ekofisk field was discovered in 1969, with production coming on-stream in 1971, and the field has since been extensively developed. The Ekofisk Bravo platform is situated to the north of the Ekofisk field and is one of two wellhead production facilities at Ekofisk. On 22 April 1977, it was the location of a blowout and North Sea's biggest oil spill.

Platform Blowout

The Ekofisk B blowout occurred during a workover on the B-14 production well, when about 10,000 feet of production tubing was being pulled. The production christmas tree valve stack had been removed prior to the job and the BOP had not yet been installed. The well then kicked and an incorrectly installed downhole safety valve failed. This resulted in the well blowing out with an uncontrolled release of oil and gas. The personnel were evacuated without injury via lifeboats and were picked up by a supply vessel.

The initial flow was estimated at 28,000 bpd with a calculated total release of 202,380 bbls. Up to 30 to 40% of the oil was thought to have evaporated after its initial release and the Norwegian Petroleum Directorate reported a total spill estimate between 80,000 bbls and 126,000 bbls.

The well was capped after seven days on 30 April 1977. Rough seas and higher than average air temperatures aided the break up of much of the oil. Later investigations reported no significant enviromental damage and no shoreline pollution. There was also no significant damage reported to the platform.

The official inquiry into the blowout determined that human errors were the major factor which led to the mechanical failure of the safety valve. These errors included faults in the installation documentation and equipment identification and misjudgements, improper planning and improper well control. The blowout was significant because it was the first major North Sea oil spill. Also significant was that the ignition of the oil and gas was avoided and that there were no fatalities during the evacuation.

Sources:

NPD: Ekofisk Field
Jan Erik Vinnem: Offshore Risk Assessment (1999)
NOAA: Ekofisk Bravo
DTI: Ekofisk B PDF document
The Times (UK) newspaper: 11 October 1977 'Human error blamed for oil rig blowout'

Photos
1. NPD Diary No.1 2002 PDF document