A series of failures at the Macondo well on the bottom of the Gulf of Mexico caused a gas explosion that sunk BP's Deepwater Horizon oil rig in April. The accident resulted in the worst accidental marine oil spill in the history of the industry.
Estimates reported in the journal Science found that 56,000-68,000 barrels of oil spilled into the gulf after the accident. Around 4.4 million barrels of oil spilled into the ocean from late April to July 15 when the well was capped.
British oil company BP managed to siphon around 800,000 barrels of oil off the surface of the water, leaving around 4.1 million barrels left, British newspaper The Guardian claimed.
The numbers reported in Science were estimated using video feeds from the Macondo well. Timothy Crone, one of the report's author and a marine geophysicist at Columbia University, acknowledged there were shortfalls in his analysis.
"We clearly acknowledge the limits of our technique," he said in a statement. "We're unlikely to ever know the exact figure."
BP and the U.S. government declared a process to permanently seal the well was completed Sept. 19, nearly five months after the initial explosion.