BP engineers took the first steps toward choking off the gulf oil well Wednesday night in a white-knuckle "integrity test" that could put a permanent stop to the flow of the gusher — or make the situation worse.
Federal officials green-lighted the test Wednesday afternoon after a 24-hour delay in which government scientists and outside experts demanded more information from BP about possible hazards created by the operation. They are concerned that a spike in pressure as the flow is clamped could blow oil and gas out the casing of the well and into the geological formations.
That scenario ultimately did not dissuade authorities from going forward with what could be a high-reward maneuver. Thad Allen, the national incident commander, said that, notwithstanding the concerns of scientists, he is "gung ho" about the test.
"It will be terrific news if we can shut in the well," Allen said, adding, however, "I don't want to get anyone's hopes up."
Shortly after 6 p.m., BP engineers closed the main chimney on the new "capping stack" installed atop the well Monday night. That left oil and gas surging from two other ports, known as the kill line and choke line. The protocol developed by BP and approved by federal authorities called for closing the kill line quickly, then very gradually reducing the flow from the choke line until the well flows no more.
The procedure hit a snag, however, when BP discovered a leak in the choke line. A statement by the company on Wednesday night said the leak "has been isolated and will be repaired prior to starting the test."
No oil and gas is being collected by surface ships, which suspended their containment operations Wednesday afternoon.
Federal officials and BP engineers are anxiously observing what happens to pressures in the well. A steady increase in pressure as the flow is reduced would be a strong sign that the Macondo well, drilled by the now-sunken rig Deepwater Horizon, is physically intact, and that oil and gas are not leaking into the surrounding mud and rock formations below the gulf floor.
Robotic submersibles are scrutinizing the muddy sea floor and the base of the blowout preventer for signs of oil or gas rising from below. Scientists are also using seismic and sonar instruments to monitor any possible movement of hydrocarbons in the rock formations surrounding the well.
If the well can handle the high pressures, BP could leave the well shut in, and it would not further pollute the gulf.
White House press secretary Robert Gibbs discussed the hazards of the test Wednesday.
"If the structural integrity of the well bore isn't strong, what you'll get is oil ... coming out into the strata," he said. That could mean leaks "from multiple points on the sea floor."
If the pressure readings are too low, BP will abandon the test. The well will be reopened and gush anew. BP would then resume trying to capture as much leaking oil as possible, using lines to surface ships and a new "top hat" on the gusher, while continuing to drill a relief well that could kill Macondo with mud and cement.
With the test imminent, BP paused Wednesday in its effort to drill the first relief well, which is only 4 feet away, laterally, from the Macondo well, which blew out April 20, killing 11 workers. The decision to halt work on the relief well was a precautionary move to ensure that hydrocarbons don't surge into the new hole from the Macondo well during the integrity test, BP senior vice president Kent Wells said Wednesday. Work on the relief well will resume when the test ends, he said. The drilling of a second relief well had already been suspended, pending results of the first relief well.
The final run-up to the integrity test highlighted the awkward relationship between BP and the federal government. The government has authority for all major decisions in the spill response, but BP has the technological expertise for the deepwater engineering. BP had planned to proceed with the test Tuesday, but federal scientists called time out, asking for more assurances that the oil company had thought through what might go wrong.
Allen said Wednesday that during the "top kill" attempt to stop the leak in May, the pressure in the well never surpassed 6,000 pounds per square inch. That befuddled engineers, who did not know where drilling mud, furiously pumped into the blowout preventer from surface ships, was going. They wondered if it was flowing through breaches in the well casing into the geological formation. The other possibility was far more benign: All the mud may have spewed out the top of the well through cracks and openings in the collapsed riser pipe.
He has said that, if all goes right, the pressure in the well during the integrity test will rise to about 8,000 or 9,000 pounds per square inch and stay there.
The test is officially slated to last 48 hours. Only at that point, Allen said, will officials decide how to proceed.