Gulf oil spill: BP begins closing valves on leaking well and monitoring conditions
BP engineers have begun to slowly close the last open valve on the cap installed above the company's leaking Gulf of Mexico well, which means that a critical integrity test is underway to determine if the well is in good enough shape to be sealed in at the top.
At about 11:30 a.m., live feeds from the BP website showed that oil was still gushing out of the last open oil line, called a choke line. Officials plan to slowly close this last line over the next few hours, taking pressure readings as they go.
Once the cap is sealed, the test could last 48 hours or longer. BP and government officials have agreed to analyze data and compare notes every six hours.
Key information about the condition of the well could be available by the end of the day and may offer hints about whether the oil may finally stop flowing.
Experts will closely monitor pressure measurements. Low pressure may indicate that the well is leaking oil from other locations. If that is the case, the cap could exacerbate the flow from cracks in the well. In the worst-case scenario, oil could rise to the sea floor, creating new surface leaks.
BP officials said that if they detect low pressure, they will unseal the cap and revert to their oil collection plan, using a series of pipes leading to containment ships on the surface.
But if the pressure readings are consistently high for 48 hours -- indicating that they well may be strong and intact -- BP may keep the cap completely sealed. That decision will not be made immediately, however.
After 48 hours, Allen said, BP will go back to taking up the oil using the pipes and containment ships. Then, Allen said, a seismic test of the sea floor will be conducted "to see if there are any areas where pockets of oil may have formed as a result of being forced out of the well bore."
-- Richard Fausset in Atlanta