The blown-out Macondo well has reached a “static condition,” oil giant BP said early Wednesday, meaning that pressure inside the well has been brought under control through a mud-pumping process that began Tuesday afternoon.
BP called the achievement “a significant milestone” and said it stopped pumping mud into the well after about eight hours because the effort had been successful.
“The well is now being monitored, per the agreed procedure, to ensure it remains static,” the company said in a statement. “Further pumping of mud may or may not be required depending on results observed during monitoring.”
Federal officials huddled in BP’s operations center are trying to manage expectations, saying that even if the static kill goes as hoped, the well at the bottom of the Gulf of Mexico won’t be kaput until it is intercepted and cemented by a relief well that’s been three months in the drilling.
“You want to make sure it’s really dead dead dead. Don’t want anything to rise out of the grave,” Energy Secretary Steven Chu told The Washington Post late Tuesday afternoon.
Meanwhile, the government is set to announce Wednesday that about 75 percent of the oil spilled from the well has already evaporated, dispersed, been captured or otherwise eliminated, The New York Times reported. The newspaper said that a government study, to be released Wednesday, will say that the remaining oil is breaking down rapidly and seems unlikely to pose significant additional harm.
According to the most recent estimates, 4.9 million barrels, or 205.8 million gallons, of oil has spilled into the gulf since the April 20 explosion of the Deepwater Horizon rig. Those estimates make this spill the largest unintentional oil spill in history.
BP initiated the process of pumping mud into the well at about 4 p.m. Tuesday. The static kill is not a quick operation by design, pumping mud at a leisurely rate of 2 barrels per minute. Engineers calculated that about 2,000 barrels would be needed to fill the well.
Ideally, the heavy mud will have caused the pressure in the well to drop to zero — but that alone won’t mean the well is dead, according to federal scientists. The well could be playing dead. For example, when the mud travels into the hot environment of the rock formation 2 1/2 miles below the seafloor, the heat could cause the mud to change form and allow the Macondo reservoir to “push back,” as Chu put it.
“You can imagine the hydrocarbons begin to finger through the mud,” he said Tuesday.
BP said it may want to follow the mud with a cement plug, but federal authorities would have to sign off on that move. There are scenarios in which a cement plug in the wrong place could complicate the process of drilling the relief well, Chu said.
Even if cement is shot into the well from the top, the relief well will still intercept Macondo sometime in the coming weeks, and will ensure that nothing is flowing upward from the reservoir, retired Coast Guard Adm. Thad W. Allen, the national incident commander, said Tuesday.
“The relief wells are the answer. There is a limit to how much we know and can find out from the static kill,” Allen said.
After a roughly 24-hour delay to deal with last-minute leaks in equipment both at the surface of the gulf and at the seafloor, BP engineers started their operation with a diagnostic test. They injected heavy oil into the well and closely observed what happened to the pressure. It rose only slightly, about 40 pounds per square inch, according to Tom Hunter, one of the scientists on Chu’s team. Then the pressure dropped in a manner indicating that the heavy oil was forcing the lighter hydrocarbons back down into the source rock.
Thrilled by that result — “the injectivity test was textbook,” said BP senior vice president Kent Wells — the engineers started the mud shot.
The static kill may be destined for a murky result rather than a clean, silver-bullet termination of Macondo. The basic problem is that the well is not a simple hole in the seafloor. It’s a hole with steel casing, seals, “shoes,” and perhaps a damaged drillpipe threading the center. Although three and a half months have passed since the explosion on the Deepwater Horizon rig, no one has yet been able to discern with any precision the condition of the well below the gulf floor.
The oil and gas could be traveling up the central casing. Or they could be coming up through the annulus, the space between the casing and the broader casing that lines the well. Conceivably, they could even be moving between the casing and the rock wall of the well. The engineers and scientists will study the data, such as the pressure readings and the amount of mud injected, and try to match it with different scenarios for the well’s configuration at depth.
“We’re looking at numbers,” Chu said. “We’re talking about what this data means as it comes. . . . The news was so good initially, we thought, ‘Maybe it’s too good, maybe the mud’s leaking out somewhere else.’ ”
There’s a lot of interpretation going on, Chu and Hunter said. The goal, they said, is to stretch the mind to imagine other possible explanations for the data, and to stay alert for erroneous assumptions.
“It’s like everything else you do in science,” Chu said.
“We’ve been doing this in our heads for weeks now,” Hunter said.