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# West Vanguard

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5. Ocean V Krist i Rig: Smedvig West Vanguard Semi-Sub Date: 06 October 1985 Location: Haltenbanken, Norwegian Continental Shelf Operator: Statoil

West Vanguard Blowout A ccording to Norwegian Petroleum Directorat e records, Statoil's well 6407/6-2 was spudded by the Smedvig West Vanguard on 04 October 1985. The 36" top hole had been drilled down to 323m MDBRT with the 30" c onductor set at 318m MDBRT. The blow-out preventer (BOP) had not yet been installed.

A t around 2050 hours on the night of 06 October1985 while drilling the upper Pliocene sediments of the 26" section, a drilli ng break was observed between 505-508m MDBRT with an ROP increase from 40m/hr to 712m /hr. Drilling was st opped at 523m MDBRT and the bit was pulled back 15m, after which the well began flowing and unsuccessful attempts were made to kill the well by pumping killm ud. The bit had entered a shallow gas pocket at around 504m causing the well to blow out. A MAYDAY was sent from the rig at about 2310 and picked up by the Norwegian rescue center at Sola, which directed rescue ships and helicopters to the crew's aid.
With no BOP used for the top hole section, the flow of gas had been directed through the diverter system. This system was unable to c ontain the flow and the liberated gas exploded at around 2320 hours, engulfing the rig in a firebal l. The one fatality is assumed to have resulted from this explosion, although reports indicate the victim's remains were neve r found. The rest of the crew were able to evac uate the rig in a matter of minutes using the fore lifeboats. The rig's deck structure, tw o of its legs and the engine room were damaged in the blast, resulting in the rig listing by 10 degrees.
By the following day, the fire had burnt out but gas continued to leak out of the well and bubble up to the side of the list ing, fire-damaged hulk. Reporters flying over the rig noted a lar g e hole in one of the ri g 's le g s, extensive fire dama g e and a fallen crane.
After the accident, the rig was towed to Freifjorden near Kristiansund, Norway and investigated by Norwegian police and SINTEF (a Norwegian industrial research institute). The investigation revealed that gas initiall y leaked from the gasket between the riser and the slip-joint, forming a gas cloud on the cellar deck level which migrated into the shaker house via a poorly closed valve and travelled through an exhaust pipe, across the upper deck and into other rooms via air ducts bef ore igniting. To quot e the SINTEF report: 'Doors and hatches in and around the drilling module on the upper deck were knocked open in a pattern that gave indications of the course of explosions.' . The subsequent failure of the diverter system was attributed to the extrem e flow of gas, drilling mud and sand, which eroded holes in pipe bends of the diverter system . Spurts of sand against the metal of the rig were suggested as one of the possi ble ignition sources of the gas cloud.
The rig was restored, returned to work and subsequently sold by Smedvig to Diamond Offshore Drilling Ltd. for US $ 68.5 million in December 2002. The rig was then renamed Ocean Vanguard, to fall in line with Diamond's rig naming policy.

Historical Footnote After the blowout, Bergen Underwater Servic es (BUS) were contracted to locate the Vanguard's eight anchors, which had been cut and discarded to allow the Vanguard to be moved away from the gas blowout. BU S then deployed an underwater ROV from the M/V Arctic Surveyor to find the anchors. During the sear ch, the ROV operator found a crashed 

### Pa g e 1 of 2 West Van g uard Blowout - Oil Ri g Disasters - Offshore Drillin g Accidents

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_ sims/ri g /van g uard.htmWorld War II Heinkel He 115 on the seabed, which had been based at Trondheim, Norway during the Second World War. The plane had been cut in to two by the movement of one of the Vanguard's anchors. The full story of the Heinkel can be read at the NUAV Norway During WWII website.

Sources: Norwegian Petroleum Directorate: West Vanguard well details SINTEF: West Vanguard report The Times (UK): 08 October 1985 'Crew flees blazing Norwegian oil rig' HSE: Review of issues associated with the stability of semi-submersibles NUAV crashed Heinkel story

Photos: 1. Fleumer Aerophoto 2. Canadian Wellsite Gallery 3. Universitetet I Tromso: Chapter 11 4. UWPhoto ANS agency 5. Jan Ove personal website

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### Pa g e 2 of 2 West Van g uard Blowout - Oil Ri g Disasters - Offshore Drillin g Accidents

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_ sims/ri g /van g uard.htm