|ODECO Ocean Odyssey Semi-Sub|
|22 September 1988|
|Shearwater Field, Block 22, UK Continental Shelf|
|Arco (now a subsidiary of BP)|
Completed in March 1983 by Sumitomo Heavy Industries in Japan for ODECO, the Ocean Odyssey was one of the most advanced semi-subs of its day and was designed to work on high pressure wells in harsh environments, such as offshore Alaska and the North Sea. It featured enclosed deck areas and derrick for working in cold areas, with a reinforced column construction and caged riser. The rig worked from April 1983 to September 1985 off the coasts of Alaska and California before being stacked for two years in Seattle, WA. The rig was then contracted to ARCO and shipped to the North Sea by February 1988.
By the summer of 1988, the rig and its crew were busy drilling the exploratory well 22/30b- 3 in the Central Graben of the North Sea. By 21 September 1988, 8-1/2" hole had been drilled to 16160 feet but drilling had been curtailed as the crew attempted to cure severe losses. At about 0530 on the morning of 22 September 1988, with limited mud and barite supplies left and against the judgement of others on board, the ARCO representatives chose to pull out of the hole to try and regain circulation. Up to 70 barrels were gained by 0900 hours as the bit was tripped out to 13200 feet, at which point the ARCO rep decided to stop and circulate. Subsequent gains led to attempts at well control via the choke.
At around 1130 hours, a rapid rise in casing pressure was seen, with substantial mud returns and the presence of gas vapour at the rotary table. With the bit at 13200 feet, the circulating pressure was not great enough to prevent a gas influx into the well and the well began to flow. The control room operator was then alerted to a gas kick and all rig crew were ordered to lifeboat stations as a precautionary measure. At around 1255 hours, the first explosion occurred and the four remaining crew on the drillfloor evacuated to lifeboats. The well was not shut in completely with the lower rams. At around 1305 hours, catastrophic choke hose failure caused by the uncontrolled flow of aggressive fluids through the choke hose led to the release of large quantities of gas and caused fires both on the rig and on the surface of the sea beneath the rig.
At some point between mustering at the lifeboats at 1130 hours and the first explosion at 1255 hours, the off-duty radio operator was ordered by the OIM to leave his lifeboat and return to the radio room to continue communications. He subsequently died from the effects of smoke and fire at around 1320 hours in the pilot house, while trying to evacuate the rig.
Of the 67 crew on board, 58 were evacuated by TEMPSC lifeboat with eight others jumping directly into the sea after missing the launching of the lifeboats, where they were picked up by fast rescue craft from the Notts Forest, the Odyssey's stand-by vessel. Crew members in the lifeboats reported waiting with the boat hatches open for the remainder of the crew until the first explosion occurred and boat launching began. The four drillfloor crew arrived at the boats at this point and jumped in through the hatches of the boats, just as the survival-suited occupants were frantically trying to close the hatches as a wall of fire approached.
After the event, a Fatal Accident Inquiry was held at Aberdeen's sheriff court, which was critical of both the OIM and ARCO's handling of the incident:
'The death of Timothy Williams might reasonably have been prevented (i) if the Offshore Installation Manager (OIM) had not ordered him from the lifeboat to the radio room; (ii) if the OIM, having ordered Timothy Williams back to the radio room, had countermanded that order when the rig was evacuated, and taken steps to see that the countermanding order was communicated to him'.
It was also concluded that the ARCO representatives had not followed safe and correct drilling practices in the management of the well, which included failing to correctly identify shut-in drillpipe pressure, failing to correctly calculate the circulation time of the gas kick and failing to shut in the well once the well began flowing uncontrollably.
For a number of years after the Odyssey accident, the UK Dept. of Energy effectively banned drilling in areas with anticipated reservoir pressures in excess of 10,000 psi.
After the fire, the Odyssey's story takes an interesting turn. It was berthed at Dundee docks in the UK for some time before being redeveloped as an ocean-going satellite launch pad called Sea Launch by a joint four-company consortium which included Boeing and Kvaerner. Sea Launch is based at Long Beach, California where the spacecraft are assembled before the rig is relocated to the equatorial Pacific Ocean for launch.
R. D. Ireland (1991). 'Ocean Odyssey Fatal Accident Inquiry', Aberdeen Sheriff Court
HSE Ocean Odyssey Emergency Evacuation
DTI Strategic Environmental Assessment of the Former White Zone
Official Sea Launch Website
1. Canadian Wellsite Gallery
2. Japanese Assoc. for Petroleum Technology
4. Sea Launch website