BP Begins ‘Top Kill’ to Stop Oil Flow from Broken Well
HOUSTON, Texas, May 26, 2010 (ENS) – BP started the “top kill” operations today to stop the flow of oil from the damaged Deepwater Horizon wellhead in the Gulf of Mexico.
The procedure is intended to stem the flow of oil and gas and ultimately kill the well by injecting heavy drilling fluids through the blowout preventer on the seabed, down into the well.
Federal On-Scene Coordinator U.S. Coast Guard Rear Admiral Mary Landry and the Unified Area Command, acting on the validation of government scientists and in consultation with the National Incident Commander Admiral Thad Allen, gave approval to proceed with the top kill operation.
A diagram of the top kill procedure (Image courtesy BP)
Pumping started at 1 pm local time and continues. BP officials estimate a 60-70 percent chance of success for this procedure and a time frame of 24-48 hours before we’ll know if the procedure worked.
This top kill procedure has not been carried out offshore at 5,000 feet water depth before, and its success cannot be assured, the company said in a statement.
The primary objective of the top kill process is to put heavy kill mud into the well so that it reduces the pressure and then the flow from the well. Once the kill mud is in the well and it is shut down, then BP intends to follow up with cement to plug the leak.
For the top kill procedure, BP had to design equipment to pump the highest possible kill, regardless of the flow rate of oil from the well, to force a downward flow of mud into the well. “This is very complex and involves several complex procedures coming together,” the company said.
Should it be necessary, plans and equipment are in place to combine the top kill process with the injection under pressure of bridging material that the company has called “junk shot” into the blowout preventer to stop or limit flow of oil.
“Throughout the diagnostic process and top kill procedure very significant changes in the appearance of the flows at the seabed will be expected,” said BP. “These will not provide a reliable indicator of the overall progress, or success or failure, of the top kill operation as a whole.”
BP senior vice president Kent Wells told reporters the company has been planning to conduct the top kill procedure from April 22, the day the Deepwater Horizon sank to the seafloor, leaving the broken wellhead spilling oil into the gulf.
“We’ve been designing the top kill from day one,” said Wells. “In terms of understanding enough information to understand the equipment and get it in place, it’s been happening at a pace far faster than we could typically implement.”
A total of 50,000 barrels of mud is on location to kill the well. BP says that amount is far more than necessary, “but we want to be prepared for anything.” Pumping capacity on location is more than 30,000 hydraulic horsepower.
The mud will be pumped down the 6-5/8 inch drill pipe then through three-inch hoses, which go through the manifold on the seafloor. Then the mud moves through another set of three-inch hoses attached to the Deepwater Horizon blowout preventer’s choke and kill lines.
Should the top kill not succeed in fully stopping the flow of oil and gas from the well, BP then intends to deploy a lower marine riser package, LMRP, cap containment system.
Deployment of this system will involve first removing the damaged riser from the top of the blowout preventer to leave a cleanly-cut pipe at the top of the blowout preventer’s lower marine riser package.
The LMRP cap, an engineered containment device with a sealing grommet, would then be connected to a riser from the Discoverer Enterprise drillship and then placed over the existing LMRP with the intention of capturing most of the oil and gas flowing from the well.
The LMRP cap is on site and BP anticipates that this option will be available for deployment by the end of May.
Additional options also continue to be considered, including the option of lowering a second blow-out preventer, or a valve, on top of the failed Deepwater Horizon blowout preventer.
Work on the drilling of two relief wells, begun on May 2 and May 16, continues. Each of the wells is estimated to take some three months to complete from the commencement of drilling.