By ERIC NALDER and LINDSAY WISE
HOUSTON CHRONICLE
May 4, 2010, 10:03PM
Minutes before the Deepwater Horizon exploded in fire, workers on the deck heard a thump, then a hissing sound. Gas alarms sounded and the rig shook.
Seawater and mud containing gas from the well spewed up through the crown of the derrick and rained down on the drilling floor; fumes reportedly moved into the “safe zones” where the electric generators are located. The generators raced out of control as they sucked gas into the air intakes.
When the electric power surged, light bulbs exploded, computers and other electric systems were destroyed, leaving the rig in darkness except for the light from fires and explosions that ripped apart walls, according to accounts derived from interviews with attorneys representing survivors, missing rig workers and their families, as well as experts in the field of offshore drilling operations.
Before the blowout, the rig's crew had been replacing heavy and valuable drilling mud with lighter salt seawater in the top section of pipe known as the riser — the purpose being to extract the mud so they could remove the riser, several sources said. While doing so, they had to secure the wellhead to keep oil and gas from blowing out.
But blow out it did.
Kevin Eugene, a steward on the rig, said he was in his bunk watching TV about 10 p.m. when a “big old loud boom” and an alarm went off “almost simultaneously.”
The lights went out. The platform began shaking.
“I thought the place was falling in the ocean, that the whole rig was collapsing,” said the father of four from Slidell, La.
Ceiling tiles, dust and debris rained down from overhead. Clad only in his pajama pants and undershirt, he scrambled down a hallway toward an exit to a stairwell that would lead to a lifeboat up on deck. He heard more explosions, but can't remember how many.
When he got onto the deck, he felt a blast of heat and saw flames about 200 yards away.
“I mean it was the hugest, biggest fire I've ever seen,” Eugene said. “It was just a big old ball of fire up there on the derrick. The whole derrick was on fire. The fire was shooting from out the well over there that the derrick was connected to and you could hear the gas gushing out.”
The deck was covered with oily mud.
Blowout preventer failed
All these things — the mud, the alarms and the job that was being done that day — will be key in determining why the Deepwater Horizon exploded, and ultimately sank, killing 11 and causing one of the nation's worst oil spills in the Gulf of Mexico.
Alarms designed to detect escaping gas sounded on the drilling floor minutes before the eruption, said attorney Ronnie Penton of Bogalusa, La., whose client, a rig worker, escaped by jumping off the rig and whose job included maintaining the alarms.
When the alarms go off “you shut it down,” said Daniel Becnel, an attorney from Reserve, La., who has filed lawsuits on behalf of fishermen, oystermen and other Louisiana residents claiming damages from the spill. “They've got panic switches all over the place.”
Those switches are supposed to activate a blowout preventer on the ocean floor, a huge and complex tower of valves and pipe crimpers designed to shut down a well in an emergency. It didn't work.
Although it had been tested beforehand, BP now says robot submarines have discovered at least one problem with the blowout preventer, though it is unclear whether it caused the malfunction.
“We have found that there are some leaks on the hydraulic controls,” said Bob Fryar, senior vice president of BP's exploration and production operations in Angola, in southwestern Africa.
Investigations will be done by the Minerals Management Service, the U.S. Coast Guard, plaintiffs' attorneys, BP and others. The probes likely will focus in part on whether all safety standards were followed, or whether any critical shortcuts were taken.
Daren Beaudo and David Nicholas, spokesmen for BP, said any comment on the circumstances prior to the blowout would be “premature.”
Guy Cantwell, spokesman for drilling rig owner Transocean, also declined to go on record, saying: “At this time we cannot get ahead of ourselves with respect to the facts of this incident, and to do so would be speculation.”
It wasn't an ordinary day
On April 20, at 11 a.m., the day's procedures were laid out at a crew meeting on the rig, according to Penton, and it wasn't going to be an ordinary workday.
BP was temporarily abandoning the well. The Deepwater Horizon was being detached from the well to be moved to another location, as soon as the next day. And the well was being capped.
Experts say well-capping poses special hazards. One arose that day as crews were replacing the mud with seawater in pipes going from the ocean floor to the rig.
Deep gases exert astounding upward pressure on a well. “Drilling mud,” a heavy fluid used to lubricate the drill and bring up bits and pieces of rock, is used as the main line of defense against the upward pressure, or a disastrous eruption of gas.
The mud was being displaced so the riser could be detached from the rig and the wellhead, and the well could be capped with a final cement plug. But seawater is much lighter than mud. The pressure the riser was applying to the well would have lessened by as much as 38 percent, experts said.
That could prove significant.
Investigators likely will be considering whether the drill hole and the casing pipe were secured properly with cement a day earlier.
“The big question is how confident were they in the casing cementing job,” said Elmer “Bud” Danenberger, who recently retired as chief of offshore regulatory programs for the Minerals Management Service. “They shouldn't have begun this (riser) operation until they were confident in that.”
Cementing job tested
Cementing problems have caused other blowouts, including a major one last August in the Timor Sea and up to 18 in the Gulf of Mexico since 1992, documents show.
Directed by BP, Halliburton had cemented the well below the Deepwater Horizon 20 hours before the blowout, presumably enough time for the cement to properly set. Halliburton said in a written release that it had properly tested the effectiveness of the cement job, but it did not reveal those test results.
Questions are being raised about those tests, and about everything from the nature of the fluid used to push down the plug to the chemistry of the cement itself.
Also at issue will be other plugs in the well. Halliburton said the final cement plug at the top of the well had not been installed because “operations had not yet reached the point” requiring it.
Penton said his client told him that the “seal assembly” — an important plug down in the well — had been set less than a half hour before the blowout.
“This was a modern marvel,” said attorney Richard Arsenault of Alexandria, La., referring to the high-tech Deepwater Horizon, built in 2001 and insured by Transocean for $560 million. “If that kind of technology can't prevent this kind of disaster, that's very troubling.”
ernicnalder@hearst.comlindsay.wise@chron.com 
