Macondo top kill begins : BP admits crucial error
BP admits to the crucial error happened hours befor the explosion to the investigators and also informed about the top kill procedure progress. The company told congressional investigators that pressure tests on a drill pipe hours before the deadly explosion that caused the Gulf of Mexico oil leak flagged up a “fundamental mistake,” a memo released by congressmen Henry Waxman and Bart Stupak said.
The company said that the operation, which will pump heavy mud down the wellbore in an attempt to gain control of the oil flow and ultimately kill the well has already begun. Earlier, BP chief Tony Hayward gave the top kill procedure a 60 per cent to 70 per cnet chance of success.
The fundamental error the BP official referred to concerned the results of a negative pressure test. According to the investigators, two hours before the explosion, as preparations were made on the Transocean semi-submersible deepwater horizon to start negative pressure testing of the wellbore, the system gained 15 barrels of liquid rather than the five that were expected, indicating there may have been influx from the well. A cementer witness was quoted as saying. “The well continued to flow and spurted.”
The investigator said the pressure test was then moved to the kill line, where a volume of fluid came out when the line was opened. It was then closed. At this time, pressure began to build in the system to 1400 pounds per square inch. The line was opened and pressure on the kill line was bled to 0 psi, while pressure on the drill pipe remained at 1400 psi.
The BP investigator said this indicated a “fundamental mistake” may have been made here as this was an “indicator of a very large abnormality.” However, once the pressure was bled off, work continued as normal – the line was monitored and by 7.55pm the rig team were apparently satisfied the test had been successful and started displacing the remaining downhole fluids with seawater.
It is not made clear yet as who made decisions after the problem was found. BP and rig owner Transocean both had supervisors on the rig when it exploded.
Details of events leading up to the blowout come as new information from the leaking well seems to confirm widely held suspicions within industry that problems with cementing played a key role in the 20 April explosion.
BP performed diagnostic testing of the BOP – a move which will determine how the UK supermajor will design the top kill of the Macondo well or whether the procedure will work at all. Company official Kent Wells said that BP staff will begin testing to see if they can actually inject mud at each of the five entry points that could be used in the top kill. The tests are expected to take 12 to 24 hours and the results will determine how BP ultimately designs the top kill operation and any future well interventions. News Agencies
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