Setback Delays ‘Top Kill’ Effort to Seal Leaking Oil Well in Gulf

HOUSTON — BP had to halt its ambitious effort to plug its stricken oil well in the Gulf of Mexico on Thursday afternoon when engineers saw that too much of the drilling fluid they were injecting into the well was escaping along with the leaking crude oil.

A technician at the BP command center said that pumping of the fluid had to be stopped temporarily while engineers were revising their plans, and that the company hoped to resume pumping by midnight, if federal officials approved.

The technician, who spoke on condition of anonymity because he was not authorized to brief reporters, said the problem was not seen as serious. “We’re still quite optimistic,” he said, but cautioned: “It is not assured and its not a done deal yet. All of this will require some time.”

Earlier in the day, officials had been encouraged that the heavy drilling fluid, known as mud, being pumped into the well appeared to be working. But the fluid had not yet overcome the upward pressure of the escaping oil and gas, according to Coast Guard commandant Adm. Thad W. Allen.

“They said this could take 24 to 36 hours, and they are in the process of monitoring it,” Admiral Allen said.

The news of yet another delay in capping the well came on a day of rapid-fire developments from Louisiana to Washington.

A report from government experts, who said that the flow of oil from the well, which has been gushing since an explosion and fire wrecked a drilling rig in late April, had been several times worse than the preliminary estimate by BP.

If these new estimates prove to be accurate, the spill would be far bigger than the Exxon Valdez disaster in 1989 and the worst in United States history.

As frustration and criticism surged over the Obama administration’s handling of the crisis, the head of the agency that oversees offshore oil drilling, S. Elizabeth Birnbaum, resigned under pressure on Thursday after only 10 months in the job.

Hours later, in a lengthy news conference, President Obama defended his administration’s response to the spill, while acknowledging some shortcomings in estimating the flow of oil.

“Those who think we were either slow on the response or lacked urgency, don’t know the facts,” Mr. Obama said. “This has been our highest priority.”

He acknowledged that his administration could have pressed BP sooner to produce a better estimate of the flow of oil leaking from the well. A panel of experts said Thursday that the well has been spewing 12,000 to 19,000 barrels of oil a day, far more than previous estimate of 5,000 barrels a day. .

In response to several questions about Ms. Birnbaum’s resignation on Thursday, Mr. Obama said he had not had a chance yet to discuss the matter with Ken Salazar, the interior secretary, who was testifying at Congressional hearings most of the morning.

Even as BP watched the progress of its well-plugging measure and Mr. Obama spoke about the government’s role in managing the crisis, oil continued to find its way ashore in Louisiana’s coastal wetlands.

Coast Guard Admiral Thad Allen on Thursday approved portions of Louisiana’s $350 million plan to use walls of sand in an effort to protect vulnerable sections of coastline. The approved portion involves a two-mile sand berm to be built off Scofield Island in Plaquemines Parish, La. — one of six immediate projects proposed by Gov. Bobby Jindal. “What Admiral Allen told us today is that if the first one is effective, then they will consider moving on to the next one,” Mr. Jindal said at an afternoon news conference in Fourchon, La.

“We know this is going to work, and we’re calling on our federal government to make BP build the next five,” he added. “Now it’s clear from the task force that there’s even more oil that’s in the water. That shows the urgency to get this built to protect our wetlands, our marshlands.”

Early indications on Thursday were positive for the well-plugging measure, known as a top kill. Crews were injecting heavy drilling fluid deep into the well in hopes of stemming the relentless flow of gas and oil, which has devastated commercial fishing in the Gulf for five weeks, fouled miles of coastline and put the company and federal regulators at the center of a political firestorm. Several previous attempts to stop the leak had failed.

BP warned when it began the top kill on Wednesday that success was not guaranteed and that it could still fail at any moment. BP was guarded in its official statements on Thursday morning, saying only that the top kill was proceeding and that there were “no significant events” to report.

Still, there were indications Thursday morning that the heavy fluid, called mud, was slowly building up within the well bore, as engineers hoped it would when they began pumping it from surface ships through pipes on the sea floor.

At first, most of the mud was carried away by the oil and gas streaming up through the well at high pressure, but with enough mud being pumped in at a fast enough rate, it started accumulating inside the well. The hope is that eventually enough mud will accumulate to overcome the upward pressure of oil.

The technician working on the measure said early on Thursday that the vast amount of data collected had been initially positive. Planning had already begun for cementing the well, the next step in sealing it after the flow of oil and gas is stopped by the drilling mud, but that step would not be undertaken until the injection of fluid had “completely killed the well,” and the oil flow had stopped. Then approval will be needed from the Coast Guard and federal agencies to move forward, the technician said.

A panel of experts assessing the rate of flow of the oil since the disaster began gave a best estimate on Thursday that was 2.4 to 3.8 times the estimate of 5,000 barrels a day offered for weeks by BP. The company had warned that its estimate was preliminary and not very reliable, and Dr. Marcia McNutt, director of the United States Geological Survey, said that the new range also remained uncertain.

The estimated flow rate was based in part on observations that as of May 17th, there was already probably between 130,000 and 270,000 barrels of oil at the surface of the gulf, with about the same amount burned, skimmed, dispersed or evaporated from the surface. A separate team measured the plume of oil as it flowed from the break and came up with a similar estimate of the rate of flow.