Wednesday, April 20, 2011
Rigzone Staff
by Jaime Kammerzell
A year ago today, an explosion on Transocean's Deepwater Horizon ultra-deepwater semisubmersible, positioned at the Macondo Prospect in Mississippi Canyon Block 252, in the Gulf of Mexico, took the lives of 11 men and caused the largest marine oil spill in history.
At 9:45 p.m. on April 20, 2010, while plugging the well for later production, seawater erupted from the marine riser onto the rig, shooting 240 ft into the air. A combination of mud, methane gas, and water quickly followed. The gas then ignited, causing explosions onboard. Attempts to activate the blowout preventer failed. Survivors said they had less than five minutes to escape after the alarm went off. Multiple ships attempted to put out the fire, but it could not be extinguished. After burning for 36 hours, the Deepwater Horizon sank in about 5,000 ft of water on April 22, 2010.
A total of 126 people were onboard the Deepwater Horizon at the time of the explosion. Only 115 evacuated. Those who were able to escape took lifeboats to the M/V Damon B Bankston workboat nearby, which had been servicing the Deepwater Horizon. The US Coast Guard searched for three days.
Although BP was the operator of the Mocondo field, it was working with Transocean and Halliburton to plug the well for later completion as a subsea producer. BP believes that Transocean and Halliburton share the blame for the disaster.
According to Transocean, its employees had been performing routine work and did not notice any problems leading up to the explosion. Halliburton had finished running production casing and cementing 20 hours before the blowout. Transocean's CEO, Steven Newman, pointed his finger at Halliburton when he said, "there was a sudden, catastrophic failure of the cement, the casing or both."
BP began drilling two relief wells on May 2 and May 16. In an attempt to stop the oil spill sooner, BP also tried using remotely operated underwater vehicles to close the BOP valves on the well head. This failed. BP then tried to place a 125 tonne containment dome over the largest leak to pipe oil to a storage vessel on the surface, but this attempt failed when gas leaked from the pipe and mixed with the cold water, which formed methane hydrate crystals that blocked the opening at the top of the dome. Pumping heavy drilling fluids into the BOP to restrict oil flow and permanently seal it with cement failed as well.
BP then tried positioning a riser insertion tube into the burst pipe. This worked adequately until the damaged riser could be capped on June 3rd. A washer plugged the end of the riser and diverted it to the insertion tube. Gas was flared and oil was stored on board the Discoverer Enterprise drillship. But this solution didn't last long. A second containment system, which connected directly to the BOP, was installed on June 16. The oil and gas were diverted to the Q4000 service vessel where it was burned. This worked well, so the Discoverer Clear Leader drillship and Helix Producer I FPSO joined in the effort, offloading oil to the Evi Knutsen and Juanita tankers. Two more vessels, the Seillean FPSO and Toisa Pices well testing vessels processed oil and offloaded to the Loch Rannoch shuttle tanker.
BP was pleased with this solution and announced on July 5, 2010, that it was recovering about 25,000 b/d and flaring 57.1 Mcf/d. However, the government estimated that the cap only captured about half of the leaking oil. BP made further adjustments to its cap solution and replaced the original cap on July 10 with a Flange Transition Spool and a 3 Ram Stack. On July 15, BP tested its new and improved cap by shutting off pipes that brought oil to the surface ships. This allowed the total pressure of the gushing oil to flow into the cap. The cap contained the oil and stopped the leak.
Meanwhile, BP continued to drill the two relief wells, which took four months to reach the Macondo well on September 15. BP pumped cement into the well 17,977 ft below the sea floor to permanently seal it. It took three days to complete. BP then permanently completed and abandoned the initial Macondo well as well as the two relief wells.
Though the oil has stopped gushing into the GOM, the aftermath remains today. Aside from the environmental and fishing and tourism impact, offshore exploration and production has been slow to return to pre-disaster levels. This is due mainly to governmental restraints.
On May 27th, President Obama instituted a temporary moratorium on offshore drilling in 500 ft or more of water, which also suspended drilling on 33 wells already in progress. He also implemented new standards for equipment and procedures.
The US Department of the Interior then issued tighter standards for barriers at underwater wells and BOPs on June 8, 2010. At the same time, the Interior Department started requiring CEOs of drilling companies to certify that their operations comply with the new regulations, including equipment testing and personnel training. Drilling in less than 500 ft of water resumed under the new standards. However, the deepwater drilling ban remained in effect until June 22, when a US federal judge in New Orleans lifted the moratorium saying it was "a blanket, generic, indeed punitive moratorium," as well as a potential harm to the economy, businesses and workers.
In response, Interior Secretary Salazar immediately issued a new order that contained additional information showing why the moratorium was necessary. The Interior Department defended Salazar's actions, saying Interior Secretary Ken Salazar "has merely fulfilled his continuing duty to manage the [Outer Continental Shelf] by reanalyzing the previously directed suspensions, evaluating new information on the adequacy of safety and environmental protection standards for OCS lease operations in the Gulf of Mexico, and issuing a new decision."
Interior Secretary, Ken Salazar
"Under these new rules, operators will need to comply with tougher requirements for everything from well design and cementing practices to blowout preventers and employee training," Salazar said. "They will also need to develop comprehensive plans to manage risks and hazards at every step of the drilling process, so as to reduce the risk of human error."
Though the drilling ban was lifted in October, the Bureau of Ocean Energy Management, Regulation and Enforcement (BOEMRE) didn't approve the first post-moratorium deepwater drilling permit until Feb. 28, 2011.
On Jan. 11, 2011, the White House released a report of its investigation of the oil spill. The report stated, "BP, Halliburton, and Transocean did not adequately identify or address risks of an accident…As a result, officials made a series of decisions that saved BP, Halliburton, and Transocean time and money—but without full appreciation of the associated risks."
Transocean and Halliburton attempted to sidestep the blame and pointed fingers at BP saying they were just following orders. Halliburton further criticized BP for its failure to run a cement bond log test.
In March, US Investigators, who hired Det Norske Veritas (DNV) to examine the failed blowout preventor, released a report that found a piece of drill pipe that was trapped inside the blowout preventer kept it from closing. The report didn't blame BP, Transocoean or Halliburton for the equipment failure. It simply focused on the cause of the failure.
According to a Reuters report from April 3, 2011, BP will be resuming its operations in the GOM in July 2011. The operator will be restricted to maintaining or increasing production on existing platforms. BP will not be permitted to drill exploration wells.
LINK
The Gulf of Mexico Oil Spill
Latest Deepwater Horizon Headlines
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