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Methane Breached Faulty Seal, Caused Rig Blast, Professor Says

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By Mark Chediak

May 8 (Bloomberg) — Bubbles of methane gas burst through a cement seal that was probably faulty, leading to the fatal explosion aboard the Deepwater Horizon rig and subsequent oil spill in the Gulf of Mexico, said a California professor who reviewed transcripts of interviews with blast witnesses.

Workers, who did basic pressure testing on the seal, didn’t perform a second and more expensive test to ensure that BP Plc’s Macondo well was properly plugged, said Robert Bea, a University of California Berkeley engineering professor.

Bea, who held engineering jobs at Royal Dutch Shell Plc in the 1960s and 1970s and later consulted for BP, said the seal was one of several breakdowns that contributed to the Deepwater Horizon explosion. The April 20 blast killed 11 workers and set off a leak that continues to spew an estimated 5,000 barrels of oil a day into the Gulf. The Deepwater Horizon, which London- based BP rented from Transocean Ltd., sank two days later.

The additional seal test would have taken more time, Bea said. He said Shell typically did that test during his years at The Hague-based company.

Doug Suttles, BP’s chief operating officer for exploration and production, declined yesterday to comment on Bea’s assertions, which were first reported by the Associated Press. Suttles, speaking at a press conference in Robert, Louisiana, said only that the incident is being investigated.

Government Investigation

The U.S. Coast Guard and the U.S. Minerals Management Service will begin an investigation May 11 to identify the factors leading to the incident, according to a government statement issued today.

Bea said friends in the oil industry sent him copies of transcripts from interviews with three Deepwater Horizon workers so he could give his insights on the incident.

The methane leakage occurred as workers were attempting to install a drill plug used as a second line of defense at the bottom of the well, said Bea, who serves on the National Academy of Engineers panel on oil pipeline safety.

“The cement is caulking a nail into brick,” Bea said. “You have to wait for the caulking to set.” There was no indication from the transcripts as to how long workers waited for the seal to set, he said.

Bea said he had to fight back tears as he read the transcripts, which included two written and one audio account of the hours leading up to the blast. “It’s tragic,” he said.

Methane Bubbles

Methane, which takes on a slushy, icy form at deep sea depths, probably expanded rapidly as it moved from high pressures 5,000 feet below the ocean surface to lower pressures and higher temperatures above.

“It is much like small bubbles in a champagne bottle rise and expand when a cork is pulled,” he said.

The gas pushed out seawater in the pipe above it, causing a gusher that was noticed by workers on the rig platform, according to transcripts Bea reviewed. Gas followed and was detected by workers, who tried to activate a device called a blowout preventer to seal off the well, he said.

The blowout preventer’s steel blades, known as shear rams, are supposed to slash through the pipe at the top of the well, Bea said. They may have failed because of the thickness and strength of the deepwater drill pipe, he said.

Cameron International Corp. provided the Deepwater Horizon’s blowout preventer.

Alarms that can detect an “explosive” amount of gas didn’t go off, Bea said. Escaping gas on the rig platform was likely ignited in a so-called drill mud room, where two engineers were killed instantly, he said.

“These guys are in hell, they are covered in water, mud and very explosive gas,” he said.

The transcripts showed that BP executives were in the next room, celebrating the rig’s safety record, Bea said. They suffered crushed bones and other serious injuries, he said.

–Editor: Tony Cox.

To contact the reporter on this story: Mark Chediak in Houma, Louisiana, at [email protected]

To contact the editor responsible for this story: Susan Warren at [email protected]

SOURCE ARTICLE

royaldutchshellplc.com and its sister websites royaldutchshellgroup.com, shellenergy.website, shellnazihistory.com, royaldutchshell.website, johndonovan.website, shellnews.net and shell2004.com are all owned by John Donovan. There is also a Wikipedia article.

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