BP, scientists study how to safely finish deepwater relief well

Aug. 23, 2010
Federal scientists and BP PLC studied how to best complete the relief well to kill the deepwater Macondo well in the Gulf of Mexico.

Federal scientists and BP PLC studied how to best complete the relief well to kill the deepwater Macondo well in the Gulf of Mexico.

Pressure tests indicate cement pumped during the Aug. 5 static kill procedure went into both the reservoir and the annulus, National Incident Commander and retired US Coast Guard Adm. Thad Allen said.

"How thick the cement barrier is between the annulus and the reservoir, we just don't know," Allen said. "It might be very thin, and we go and put pressure on that and we have a problem."

The well was shut in on July 15 when BP installed a capping stack. The blown-out well leaked an estimated 4.9 million bbl of which BP captured 800,000 bbl (OGJ, Aug. 16, 2010, p. 24).

Transocean Ltd.'s Deepwater Horizon semisubmersible drilled the well for BP and partners. An Apr. 20 blowout resulted in a rig explosion and fire that killed 11 people. The rig later sank.

On Aug. 14, Allen asked BP to analyze the risks and come up with a plan to prevent an estimated 1,000 bbl of oil in the annulus from possibly being released into the gulf during the bottom kill.

One concern is whether a transition spool between the Deepwater Horizon BOP and the capping stack could withstand the anticipated pressure when relief well crews pump heavy drilling fluid and cement into the Macondo well, Allen said.

On Aug. 18, Transocean's Discoverer Enterprise drillship was being brought to Mississippi Canyon Block 252 to purge the Macondo's closed system. More pressure testing was planned.

Another BOP was being brought to the scene. Engineers and scientists might decide to replace the failed Deepwater Horizon BOP before completing the relief well, Allen said.

In addition, they evaluated a second option that would involve building a pressure relief system at the Macondo wellhead, Allen said.

Accident investigators have requested the Deepwater Horizon BOP for examination. Allen said the question as of Aug. 18 was whether to remove it before or after the bottom kill.

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