As BP prepared its “static kill” procedure to close the ruptured Macondo well in the Gulf of Mexico yesterday, U.S. science and engineering teams released new estimates of the amount of oil that was released during the 87 days before the well was capped in mid-July.
Overall, the teams estimate that approximately 4.9 million barrels of oil were released from the well, of which approximately 800,000 barrels were captured by funneling leaking oil and gas to the surface where it was destroyed or collected.
The remaining 4.1 million barrels, which flowed directly into Gulf waters, make the 5,000 ft. Deepwater Horizon incident the largest, non-intentional release of oil in history, surpassing the 3.3 million-barrel Ixtoc 1 incident of 1979 (also in the Gulf of Mexico).
Using pressure readings obtained during the initial drilling phase, pressure measurements within the now closed capping stack, and modeling of the oil well and reservoir, the scientific teams estimate that 62,000 barrels of oil per day were leaking from the well at the beginning of the incident.
Depletion of the reservoir over time reduced the daily flow to 53,000 barrels per day immediately preceding BP’s temporary closing of the well on July 15. Acoustical measurements and high resolution video from underwater remotely operated vehicles were also used in the analysis.
The new estimates reflect the collaborative work of the National Incident Command’s Flow Rate Technical Group (FRTG), led by United States Geological Survey (USGS) Director Marcia McNutt, and a team of Department of Energy (DOE) scientists and engineers, led by Energy Secretary Steven Chu.
The refined estimates have an uncertainty of plus or minus 10 percent and are subject to revision pending new information.
The largest oil spill is generally considered to be the intentional release of 5.7 million barrels of crude — 1 million of which were recovered — into the Persian Gulf by Iraqi forces in order to impede American troops invading Kuwait during the 1991 Gulf War.
