Once the cap was in place, BP prepared to conduct a "well integrity test"—essentially, shutting off the flow of oil and checking pressure readings to see if a subsurface blowout would develop. In the worst case a burst of methane could liquefy and collapse the seafloor surrounding the wellhead, thereby swallowing the blow-out preventer, capping stack and all. In a frantic, overnight session the government scientists assessed that risk and, by morning, they had decided such a worst-case blowout could be prevented with early detection of a leak.
So Chu and his colleagues required BP to monitor the well's pressure continuously for the 48 hours of the test and to keep tabs on the blowout preventer, the well itself, and the underground regions around it through both acoustic and visual methods offered by two of the 12 ROVs as well as a NOAA survey ship. Should a leak of more than 20,000 barrels be detected, or if oil pressure fell below 6,000 psi—implying an underground leak that could prove catastrophic—the cap would be immediately removed.
On July 15 at 2:25 P.M. Houston time, the test began. An ROV arm turned the handle on the capping stack 10 times, cranking it closed. For the first time since April 20, no oil spewed into the Gulf of Mexico.
Is it over yet?
The pressure of the well hovered around 6,600 psi, prompting Garwin, among others, to argue for the immediate removal of the cap.
Instead, a cell phone picture of the pressure readings graph was sent to hydrologist Paul Hsieh of the U.S. Geological Survey in Menlo Park, Calif. Working through the night, Hsieh determined that, in his best modeling estimate, the relatively low pressure readings were not a result of subsurface cracks or leaks developing but rather the fact that so much oil had already spewed from the well. Its original internal pressure of roughly 13,000 psi had diminished. The cap would stay closed.
With the oil staunched, Chu allowed BP to proceed with a so-called "static kill"—another attempt to push the oil back down the well with heavy drilling mud, made much easier by the fact that the oil no longer had a clear path out of the seafloor. Drilling mud went into the well again on August 3, followed on August 4 by a 1.5 kilometer-long cement plug.
In the end, however, despite all the resources of the federal government and one of the world's largest corporations, only a second well drilled at an angle and roughly five kilometers beneath the seafloor finally intercepted the base of the Macondo well and safely sealed the reservoir with cement. The first such relief well began drilling on May 2 and reached pay dirt in the third week of September, along with a second relief well that commenced drilling on May 17—at the insistence of U.S. Secretary of the Interior Ken Salazar. "Our job basically is to keep the boot on the neck of British Petroleum," the former senator from Colorado said on CNN.
On September 19, U.S. Coast Guard Admiral Thad Allen—national incident commander for the blowout—declared that "the Macondo 252 well is effectively dead" after spilling roughly five million barrels of oil in total.
What didn't die with it is America's thirst for oil: The U.S. consumes 21 million barrels daily. As a result of that thirst, BP has asked the federal government for permission to resume deepwater drilling in the Gulf. And, until the world's use of approximately one barrel of oil per second diminishes, it is unlikely that the Macondo blowout will follow the fate of Garcia Marquez's fictional town and be "exiled from the memory of man."