The British oil company issued a statement Thursday, saying the operation was completed as part of the so-called "static kill" procedure that has also involved pumping heavy mud into the well. BP says it is monitoring the well to confirm the effectiveness of the procedure.
Offshore oil crews were expected to take several hours Thursday to pump cement into the top of BP's Macondo well to seal it off permanently. Officials approved the final phase of the so-called "top kill" operation, after crews pumped heavy drilling mud into the well to counter the flow of oil and natural gas.
Retired Coast Guard Admiral Thad Allen is the top U.S. official overseeing the response to the oil leak which started April 22. He says the cementing work will ensure the well releases no more oil into Gulf waters.
"We will have created a significant milestone and made a major step forward when the cementing is done," he said."I think we can all breathe a little easier regarding the potential we will have oil in the Gulf ever again."
Work on the damaged well is not complete, however, because crews plan to perform a similar operation at the bottom of the well. In coming weeks, drilling teams are expected to finish a relief well that will penetrate the well pipe that extends nearly four kilometers beneath the sea floor.
Admiral Allen said the relief well will be used to pump mud and likely cement into the outer section of the well, or annulus, to prevent oil from escaping.
"This well will not be killed until we do the bottom kill and do whatever needs to be done once we understand the condition of the annulus, which will most likely be [pumping] mud and cement from the bottom," he said.
Once the well is killed, more attention will shift to efforts to clean up oil residue across Gulf waters and U.S. coastline. BP crews capped the leaking well in mid-July, but officials fear more than one million barrels of oil remain in the environment.
Admiral Allen said officials are beginning to redeploy skimmer boats, which siphon oil off the surface of the water.
"We are starting to take a look at large skimming vessels offshore, and we need to collapse those back in closer to shore," he said. "We need to start focusing on areas that we already know have [oil] impacts."
The state of Louisiana has been hardest hit by the oil leak, which fouled beaches, marshland and valuable fishing grounds. Oil residue also has hit coastal areas in Alabama, Mississippi and Florida.
The oil leak began in April, when the Deepwater Horizon drill rig exploded and sank, killing 11 workers on board.