Deepwater Horizon Oil Spill Timeline

The Coast Guard discovered oil leaking from the damaged wellhead and broken riser pipe on the seafloor, roughly 5,000 feet below the surface. Initial estimates suggested around 1,000 barrels per day were escaping, an estimate that would later be revised dramatically upward as the spill's severity became clear.

Image source: Timeline of the Deepwater Horizon oil spill

Remotely operated vehicles (ROVs) made repeated attempts over several days to activate the well's blowout preventer, a 450-ton stack of valves designed to seal the well in an emergency. The device had failed during the blowout, and all attempts to trigger it remotely proved unsuccessful, leaving the well flowing freely.

Image source: Blowout preventer

The Obama administration declared the spill an incident of national significance and mobilized federal resources, deploying the Coast Guard, Navy vessels, and National Guard troops to assist with containment. Homeland Security Secretary Janet Napolitano and Interior Secretary Ken Salazar traveled to the Gulf to oversee the response.

NOAA estimated that the leaking well was releasing approximately 5,000 barrels (210,000 gallons) of crude oil per day — five times the earlier estimate. Subsequent scientific assessments would eventually conclude the actual rate was far higher, peaking at an estimated 60,000 barrels per day.

President Barack Obama made multiple trips to Louisiana, Mississippi, Alabama, and Florida during the crisis to inspect cleanup efforts and reassure affected communities. His administration faced criticism over the perceived slow federal response, drawing comparisons to the government's handling of Hurricane Katrina.

Image source: Political effects of Hurricane Katrina

BP lowered a 98-ton containment dome over the largest leak point in an attempt to capture escaping oil. The effort failed when methane gas hydrates accumulated inside the dome, clogging the pipe intended to funnel oil to the surface and rendering the structure buoyant and unusable.

BP inserted a narrow tube into the broken riser pipe, siphoning a portion of the escaping oil and gas to a surface vessel for processing. At its peak, the tube captured roughly 2,000 barrels per day — only a fraction of the total flow, but the first partial success in containing the spill.

BP attempted a 'top kill,' pumping heavy drilling mud into the well at high pressure to overcome the upward flow of oil, followed by cement to permanently seal it. After three days, BP announced the procedure had failed, dashing hopes for a quick end to the spill and intensifying public frustration.

Using robotic saws to cut away the damaged riser, BP installed a lower marine riser package (LMRP) cap over the wellhead. The cap gradually increased its collection rate, eventually capturing the majority of the escaping oil through a drillship on the surface until the well was fully sealed.

BP pumped heavy drilling mud through the newly installed cap into the well in a 'static kill' operation, forcing the oil back down into the reservoir. The procedure succeeded in stabilizing the well, paving the way for the final permanent sealing via the relief wells.

After months of drilling, the first relief well intersected the Macondo well at a depth of about 13,000 feet below the seafloor. Crews pumped cement into the annulus, and on September 19, retired Coast Guard Admiral Thad Allen declared the well effectively dead, ending the flow of oil after 87 days.

National Incident Commander Thad Allen announced that the Macondo well was 'effectively dead,' confirming that cement injected through the relief well had permanently sealed it. An estimated 4.9 million barrels of oil had been released, making it the largest marine oil spill in history.

Under the Oil Pollution Act of 1990, BP was designated the 'responsible party' for the spill, making it legally liable for cleanup costs and damages. BP committed to paying all legitimate response costs, marking the beginning of what would become tens of billions of dollars in financial obligations for the company.

Interior Secretary Ken Salazar issued a six-month moratorium on new deepwater drilling permits in the Gulf of Mexico, suspending 33 exploratory wells. The ban, later extended, drew fierce opposition from Gulf Coast officials and industry groups who warned of economic devastation, and it was challenged in federal court.

After meeting with President Obama at the White House, BP agreed to establish a $20 billion claims fund administered by attorney Kenneth Feinberg to compensate individuals and businesses harmed by the spill. The company also suspended its dividend to preserve capital for spill-related obligations.

BP CEO Tony Hayward testified before the House Energy and Commerce Committee, facing sharp criticism for evasive answers and his earlier remark that he wanted his 'life back.' Lawmakers accused BP of cutting corners to save time and money. Hayward stepped down as CEO months later, replaced by Bob Dudley.

Image source: Tony Hayward

President Obama created the bipartisan National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, co-chaired by former Senator Bob Graham and former EPA Administrator William Reilly, to investigate the causes of the disaster and recommend reforms to offshore drilling regulation.

The presidential commission concluded that the disaster was avoidable and resulted from systemic failures by BP, Halliburton, and Transocean, compounded by weak regulatory oversight. It called for sweeping reforms to offshore drilling safety practices, industry standards, and government regulation.

Image source: Deepwater Horizon oil spill

A federal court approved a class-action settlement between BP and private plaintiffs — including fishermen, hotel owners, and other Gulf businesses and residents — valued at approximately $7.8 billion. Payments continued for years, though disputes over claim eligibility led to further litigation.

BP pleaded guilty to 14 criminal counts, including 11 felony counts of manslaughter for the deaths of the rig workers, and agreed to pay $4 billion in fines and penalties — the largest criminal resolution in U.S. history at the time. Two Halliburton employees and a Transocean executive also faced charges.

U.S. District Judge Carl Barbier ruled that BP bore 67% of the blame and acted with gross negligence and willful misconduct, a finding that exposed the company to Clean Water Act penalties of up to $4,300 per barrel spilled. Halliburton and Transocean were found negligent but not grossly so.

BP reached an $18.7 billion settlement with the federal government and five Gulf states, resolving outstanding Clean Water Act penalties and natural resource damage claims. Combined with prior payments, BP's total pre-tax costs for the disaster ultimately exceeded $65 billion.