Hope was all but lost last Friday that 11 missing crew members from drilling rig Deepwater Horizon — which burned and sank in the Gulf of Mexico (GOM) — would be found, although rescuers continued to search. While some feared an environmental catastrophe, oil sheen on the water appeared to be from the explosion and not a leaking well, officials said.

Last Tuesday night the semisubmersible mobile drilling rig, which was owned and operated by Transocean Inc. on behalf of BP plc, experienced an explosion and fire. The rig was drilling an exploration well on BP’s Macondo prospect in Mississippi Canyon Block 252, 42 miles southeast of Venice, LA.

U.S. Coast Guard Rear Admiral Mary Landry, who heads the Eighth Coast Guard District, which was conducting the search, told CBS News Friday the 11 missing were most likely on the rig at the time of the explosion. We are “holding out hope that we may find one of these 11 missing people,” she said. “We’re planning to search throughout the day today, through daylight hours today.”

Of the 126 on board at the time of the explosion, 111 were accounted for. Of the 126, 79 were Transocean employees, six worked for BP, and the remaining 41 worked for third-party service providers, said Transocean Vice President Adrian Rose.

Smith International Inc. said five employees of M-I SWACO, which it owns with Schlumberger Ltd., were aboard Deepwater Horizon at the time of the explosion. Three are safe; two remained missing Friday. “We are deeply saddened by this tragic event. Our thoughts and prayers are with our colleagues and the loved ones of those affected,” said Smith International CEO John Yearwood.

Landry said the rig is not on top of the wellhead but is nearby. “At this point in time we’re confident that the sheen that we’re working with is residual from the explosion…We have not seen any visible signs of crude emanating from the well. We’ll continue to monitor that situation.”

Last Thursday BP activated an oil spill response team and is assisting Transocean in an assessment of the well and subsea blowout preventer with remotely operated vehicles, the company said. BP has also initiated a plan for the drilling of a relief well, if required. A nearby drilling rig would be used to drill the well and is available to begin activity immediately.

BP mobilized a flotilla of vessels and resources that includes 32 spill response vessels; skimming capacity of more than 171,000 b/d; offshore storage capacity of 122,000 bbl and an additional 175,000 bbl on standby; supplies of more than 100,000 gallons of dispersants and four aircraft to spray dispersant to the spill.

“We are determined to do everything in our power to contain this oil spill and resolve the situation as rapidly, safely and effectively as possible,” said BP CEO Tony Hayward. “We have assembled and are now deploying world-class facilities, resources and expertise, and can call on more if needed. There should be no doubt of our resolve to limit the escape of oil and protect the marine and coastal environments from its effects.”

The rig sank late last Thursday morning.

Deepwater Horizon was constructed in 2001. According to analysts, it would cost about $600 million to replace it today. The rig is credited with making one of the biggest oil and gas finds in the Gulf of Mexico last year — BP’s Tiber well completed in August in Keathley Canyon Block 102, 250 miles southeast of Houston in 4,132 feet (1,259 meters) of water. The well was drilled to a total depth of 35,055 feet (10,685 meters), “making it one of the deepest wells ever drilled by the oil and gas industry,” BP said (see NGI, Sept. 7, 2009).

Watchstanders at the USCG District Eight command center received a report at about 10 p.m. Tuesday of an explosion and fire aboard Deepwater Horizon, approximately 42 miles southeast of Venice, LA.

The exact cause of the explosion has yet to be reported by investigators, but speculation is that it was a well blowout.

“To my knowledge, this is the first serious blowout and fire to occur on this latest generation of deepwater drilling equipment,” said Michael Lynch, a consultant with Gerson Lehman Group. “In theory, with modern blowout control equipment, such an event is virtually impossible. But every seasoned driller knows that the possibility of deadly danger is never far away.”

AccuWeather.com meteorologists said there was a thunderstorm in the area of the oil rig explosion Tuesday night. Lightning could have potentially struck the rig, but weather as a cause for the explosion is under investigation by authorities.

The American Petroleum Institute expressed its concern for the crew members and their families and emphasized that the industry continuously works to improve the safety of its operations. “The industry is committed to a goal of zero fatalities, zero injuries and zero incidents, and every incident is both one too many and a powerful incentive to improve training, operational procedures, regulations, industry standards and technology.”

U.S. Sen. Mary Landrieu (D-LA) commended the search efforts and has called for an investigation of the incident. “Even as the rescue efforts continue, it is clear that the U.S. Coast Guard and the Minerals Management Service should conduct a swift and thorough investigation into this incident. It is critical that these agencies examine what went wrong and the environmental impact this incident has created. These findings should be reported to Congress as soon as possible.”

U.S. Sen. Lisa Murkowski (R-AK) said she was “dismayed” to learn of the rig’s sinking Thursday. “We do not yet know how this development will affect the marine environment, but I understand all emergency spill response units in the Gulf have been mobilized,” she said. “My staff and I are receiving regular briefings from the Coast Guard, the Minerals Management Service and BP. I will continue to closely monitor this situation and I have offered the full resources of my office to aid all of those affected by this tragedy.”

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