BP has restarted a pressure test on a leaking oil well in the Gulf of Mexico to prepare for an effort to cap the leak. Crews were forced to abort an earlier attempt because of a technical problem.
BP officials say they discovered the problem shortly after beginning a test late Wednesday that involves choking off the flow of oil from the underwater well.
During the operation, engineers closed a series of valves that are releasing oil and natural gas to measure the pressure inside the well pipe.
BP Senior Vice President Kent Wells says crews noticed a leak in one of the lines that funnels oil from the well head to surface ships. He said they needed to replace the so-called "choke line" to get an accurate pressure reading.
"We had a second choke on surface," Wells said. "We disconnected that choke and hub system, took it up, brought the other one down, landed it this morning. And we are once again positioning ourselves to do the well integrity test."
The process of closing all of the valves at the well head can take several hours. Officials say they might conduct the test over a 48-hour period to get as much pressure data as possible.
U.S. Coast Guard Admiral Thad Allen is overseeing the response to the oil well leak. He says teams are monitoring the procedure to determine whether it is safe to continue with the test.
"The only reason we would terminate the test quickly is if we had a very low pressure reading," Allen said. "That would be indicative of the fact that oil was being released somewhere in the well bore out into the formation. We would not want that. But as pressure continues to rise, we will continue to monitor it."
The pressure test is one of a series of tests BP engineers have used to study the condition of the well pipe that runs nearly four kilometers under the floor of the Gulf of Mexico.
BP's Kent Wells says that testing with seismic monitoring equipment suggests the well pipe is intact.
"We did not see any leakage of oil and gas that we could pick up in any of our seismic information that would indicate there is any oil leaving from the well," Wells said.
The test results will help engineers prepare for the kill operation, which involves filling the well pipe with heavy mud to stop the flow of oil and natural gas. BP officials say they might conduct that operation as early as mid-August, when a relief well is expected to be finished.