April 20-26: The well explosion, the sinking of the Deepwater Horizon, and the attempt to activate the blowout preventer
The oil company BP had been drilling an exploratory well in the Macondo oil deposit a mile under the surface of the Gulf of Mexico. The Macondo 252 well was drilled to a depth of a little over 18,000 feet (including the depth of the sea water) about 40 miles offshore from southeast Louisiana.
BP owned the well, and contracted Transocean Ltd. to drill it and Halliburton Energy Services Inc. to cement it. Transocean owned and operated the drilling rig named "Deepwater Horizon" which BP was leasing for a half-million dollars per day in a three-year contract. Transocean also owned and operated an emergency shut-off valve on the well known as a "blowout preventer" that was manufactured by Cameron.
Methane gas exploded from the well around 10 p.m. on April 20, for reasons likely due to the failure of the well's cement casing that had been completed by Halliburton the previous day. The monitoring systems had indicated problems with the pressure in the well around 9 p.m. and the pump had been shut down 18 minutes before the explosion. Propelled from a depth of 5,000 feet, traveling up toward the rig through a riser pipe, the gas caused the Deepwater Horizon to catch fire amidst a shower of a clay-water mixture used in drilling that is known as "drilling mud". For several minutes, water and mud shut from the 242-foot derrick. It stopped briefly, but then noxious black smoke shot from "a goosenecked pipe on the starboard side of the deck." This was followed by an explosion and a fireball. The derrick spat fire and mud. Workers, many severely injured, began to get into lifeboats.
At the time of the explosion, BP executives were in living quarters under the work deck. They had been on board to celebrate the Deepwater Horizon's seven years without a workplace safety accident resulting in lost time. Following Halliburton's completion of the cementing, rig workers had begun to set a second seal on the well head, and the well was anticipated soon to go into production.
Out of 126 workers on the rig, 15 were injured and 11 missing men were presumed dead: Transocean employees Jason Anderson, Aaron Dale Burkeen, Donald Clark, Stephen Curtis, Roy Wyatt Kemp, Karl Kleppinger, Dewey Revette, Shane Roshto and Adam Weise; and drilling mud supplier M-I SWACO employees Gordon Jones and Blair Manuel.
Anderson's father said the Transocean employees had been on the "drilling floor" of the rig, trying to control the pressure surging from the underwater well, when the riser exploded a few feet away from them. Elton Johnson, a witness to the accident, said that when Burkeen felt the first small explosion, he tried to lower his crane as best as possible and was running for safety when the much larger explosion hit.
The surviving 115 workers, mostly Transocean employees, were evacuated to a nearby rig. According to attorneys Steven Gordon and Kurt Arnold who represent some of them, they were held on the water for 15 hours as they watched the Deepwater Horizon burn, then escorted into a hotel in the middle of the night, where, prior to being allowed to phone their families and their lawyers, Transocean asked them to initial a statement denying having witnessed the accident or having sustained any injuries.
Despite attempts to put out the fire, the half-billion-dollar Deepwater Horizon sank two days later. The mile-long pipe known as a "riser," which had an internal diameter of 19.5 inches and had connected the Deepwater Horizon to the undersea oil well, bent and fell to the ocean floor.
According to BP and the U.S. government, the riser was not discovered to be leaking oil until April 24. For unknown reasons, the 48-foot-tall, 450-ton blowout preventer had not activated properly and had only partially sealed the well.
On April 26, remote-controlled submersible robots tried, but failed, to activate the blowout preventer valve to completely seal off the well. As BP estimated that oil was leaking at about 1,000 barrels per day (a barrel is 42 gallons), the visible oil spill stretched 80 miles across the ocean's surface. Over the next few days, it widened and moved closer to Louisiana's shore.
April 28 - Estimate increased to 5,000 barrels per day
On April 28, the U.S. government raised its official estimate of the leak to 5,000 barrels of oil per day. The next day, Homeland Security secretary Janet Napolitano declared the spill to be "of national significance," clearing the way for various types of federal assistance.
May 2 - BP begins drilling the first relief well
Using a drilling rig owned and operated by Transocean, BP began drilling a second well to intersect the first, a strategy recognized as the only permanent solution to the leak. The relief well would be a half-mile from the leaking well and was intended to intercept the leaking well at its base 13,000 feet below the seabed. After its completion, drilling mud would be injected through the relief well and into the leaking well. Eventually, the oil would no longer be able to push up past the weight of the drilling mud. The relief well was estimated to take three months to complete. A second relief well was planned as an additional precaution.
May 5 - BP plugs one of three leaks in the pipe
BP plugged the smallest of three ruptures in the riser, but this did not reduce the amount of oil spilling into the ocean. Eighty-five percent of the leaking light-sweet crude was now coming from the end that had broken off the Deepwater Horizon and lay on the sea floor, while the remainder was coming from a ruptured kink lower in the pipe.
May 6 - Oil makes landfall
On May 6, the first toxic, pink, oily seawater reached the shore of Freemason Island on the Chandeleur barrier island chain off Louisiana. In the weeks to come, thick oil would coat the shores. Hundreds of dead and dying sea turtles and birds would be recovered by wildlife officials.
By May 19, scientists and government officials and agencies around the world, including the European Space Agency, agreed that at least some oil had entered the "loop current" that circulates between the Yucatan Channel, the Florida Keys, and the Bahamas.
May 7-12 - The "top hat" method of containing the leak
On May 7, BP workers guided robots to place a four-story-high, 100-ton concrete and steel containment dome over the larger of the two leaks, with the intention of siphoning oil from the dome via a mile-long steel pipe into a tanker on the surface. This containment method had never before been attempted at such a depth. Warm water and methanol were used as antifreeze to prevent the pipe from being clogged by hydrates that form in cold temperatures and high pressure; unfortunately, hydrates filled the dome itself and the project had to be discontinued.
After the failure of the large dome to siphon oil from the major leak, BP lowered a five-foot-high dome on May 12 in case it was needed in an attempt to cover the smaller leak. The dome was kept on the sea floor but was never positioned over the leak.
May 14 - Siphoning oil through a tube
On May 14, BP engineers began using robotic submarines to insert a 4-inch tube into the ruptured riser pipe that would siphon some oil a mile upward to the surface. After two days of setbacks, the tube began to siphon oil to the surface. The volume of oil traveling through the tube was increased slowly to avoid the hydrate formation that had doomed the large containment dome.
On May 17, BP's COO Doug Suttles told NBC's "Today" show that the tube was siphoning over 1,000 barrels per day; BP reported on May 20 that this amount had increased to 5,000 barrels per day. Given that the tube was only siphoning a fraction of the spill, the leak was instantly recognized to be much larger than the previous estimate of 5,000 barrels per day.
May 26-29 - "Top Kill" and "Junk Shot"
Three attempts at a "top kill" method involved a total of 30,000 barrels of drilling mud injected into the well by a 30,000-horsepower pump at rates of up to 80 barrels per minute. Sixteen attempts at a "junk shot" involved injecting debris such as shredded plastic, knotted rope, and golf balls-referred to as "bridging materials"-into the blowout preventer.
Carried out despite the risks of further puncturing the pipes or dislodging debris that was usefully blocking the pipes, these methods unfortunately failed to stop the leak.
May 22-27 - Assessing government involvement; Estimate increased to 12,000-19,000 barrels per day
On May 22, Pres. Obama ordered the creation of a bipartisan National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling to investigate the causes of the spill and recommend precautions for the future.
In response to a challenge at a press conference on May 24 about whether BP could "get out of the way" and the government could "step in" more, National Incident Commander and Coast Guard Admiral Thad Allen pointed out that "to work down there you need remotely operated vehicles; you need to do very technical work at 5,000 feet. You need equipment and expertise that's not generally within the...federal government in terms of competency, capability or capacity."
On May 27, scientists from the U.S. Geological Survey released estimates of the leak at 12,000 to 19,000 barrels per day and declared the spill to be the largest in U.S. history, surpassing the Exxon Valdez tanker spill in Alaska in 1989. Pres. Obama ordered the suspension, until a safety review could be completed, of planned lease sales in the Gulf and off Virginia and of planned exploratory wells in the Gulf and the Arctic.
May 29 - June 3 - Cutting the riser pipe
On May 29, Rear Admiral Mary Landry directed BP to begin the new tactic of cutting the leaking riser pipe and placing a containment dome over it. BP workers immediately began to build a cap to fit the lower marine riser package (LMRP). Warm water was circulated to prevent freezing. Initially, BP said the volume of oil was not expected to increase significantly when the riser was cut.
On June 2, a diamond-edged saw was stuck in the riser for several hours. It was removed, found to be jammed, and retired, ending hopes of getting a clean cut to allow a tight seal for the LMRP. BP returned to using the giant robotic arm that successfully made the first cut in the riser the previous day. This rougher cut would accommodate a fresh attempt at the "top hat" method that had been unsuccessfully attempted on May 7. The pipe was successfully cut and capped on June 3. The cutting was subsequently believed to have increased the flow, but it was unclear by how much.
June 4-20 - Siphoning from the riser; Estimate increased to 35,000-60,000 barrels per day
After beginning siphoning from the LMRP on June 4, BP retrieved about a third of the high end of the government estimate of 19,000 gallons leaking daily. Some oil was still escaping, by design, through vents in the top of the containment dome so that cold water would not enter and form hydrates. BP planned to close the vents slowly. The maximum that could be funnelled through the containment cap was 15,000 barrels per day, a milestone reached on June 7. The next day, on NBC's "Today" Show, BP COO Doug Suttles anticipated that the implementation of an auxiliary system to siphon up to an additional 10,000 barrels per day would "capture the vast majority of this flow" and that the spill "should be down to a relative trickle" by June 14 or 15.
Instead, on June 15, the government estimate of the leak was increased to 35,000 to 60,000 barrels per day, and siphoning was suspended due to a fire aboard the drilling ship Discover Enterprise, which BP attributed to a lightning strike. Even when the second containment system began siphoning oil from the blowout preventer to another ship called the Q4000 on June 16, the total capacity of both systems was only 28,000 barrels per day.
Oil recovery was stopped again on the Discovery Enterprise again on June 18 for ten hours because a safety vent called a "flame arrester" was blocked.
Hopes were still pinned on the relief wells to provide a permanent stop to the leak.
The article above was posted to Helium Network on June 20, 2010 while the well was still leaking. Updates are provided below.
During the first week of August, a procedure called a "static kill" failed to stop the leak.
NOAA stated on Aug. 18 that 22 percent of Gulf waters remained closed to fishing.
A report in the journal Science on Aug. 19 said that the chemical ingredients of oil had been detected three miles from the leaking well and traveling southwest in the water. This was the predictable result of having used 1.8 million gallons of chemical dispersants to drive the oil away from the surface. An underwater mass spectrometer proved that it was the same oil that was leaking from the Macondo well. An article in the Washington Post called it "a 22-mile-long invisible mist of oil" that was floating between one-half mile and one mile beneath the surface. Small fish and crustaceans live there and could potentially bring the oil up the food chain.
On Aug. 21, the research vessel Oceanus departed to find where the oil was going. Scientists aboard the ship reported a few weeks later that much of the oil seemed to have settled to the sea floor, as they found "a substantial layer of oily sediment stretching for dozens of miles in all directions." Scientists described the oil as "fluffy" and "porous" and "more than 2 inches thick" and "all over the place" and containing "recently dead shrimp, worms and other invertebrates."
BP released a report of its internal investigation into the accident on April 20. It found many causes, including BP employees accepting a negative pressure reading that turned out to be wrong, problems with the cement provided by Halliburton, and a failed blowout preventer provided by Transocean.
The U.S. Department of the Interior's Bureau of Ocean Energy Management declared that the well was finally sealed. This was achieved with a "bottom kill" method that involved BP drilling a separate well that connected to the leaking well and poured concrete into it. The U.S. government believed that the accident had leaked 4.9 million barrels (206 million gallons) of oil into the ocean.
CNN recapped the previously unsuccessful methods: “The rig's blowout preventer, a massive fail-safe device at the seabed, failed to operate after the blast. Efforts to activate it using remote submarines failed. An effort to plug it with heavy drilling fluid and cement failed. A bid to jam it shut by pumping it full of debris also failed.”
The National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling produced its final "Report to the President. The report was titled "Deep Water: The Gulf Oil Disaster and the Future of Offshore Drilling."
Image above: Public domain. Taken by Petty Officer 2nd Class Justin Stumberg. U.S. Navy Photo ID 100506-N-6070S-371. Wikimedia Commons.