Gulf oil valve 'blunder' revealed
Critical time was wasted during initial efforts to slow the Gulf of Mexico oil spill due to a safety valve being wrongly plumbed, a senior BP official has claimed.
Harry Thierens, vice president at the oil giant, told a US panel he was "astonished" to learn that the blow-out preventer was changed by contractor Transocean.
It meant that the work of underwater robots trying to trigger the device was futile in the early days after the accident.
The April 20 blow-out in the Gulf of Mexico resulted in the deaths of 11 workers and the worst environmental disaster the region had ever seen.
Since the accident, BP has come under attack over allegations it prioritised speed and cost-cutting above safety. But an investigating panel in Houston, Texas, heard testimony suggesting rig contractors Halliburton and Transocean may also be at fault.
It emerged during Mr Thierens' evidence that Transocean, hired by BP to drill the well, had difficulty providing details of the changes it made to the blow-out preventer, even after it emerged that they were made.
On April 25, five days after the explosion, Mr Thierens wrote in his logbook: "Some confusion in TEO (Transocean), regarding details around the control system. No Transocean approved drawing available."
It later emerged that the device suffered other problems, including pipes being run to different places.
This meant that the early work by the underwater robots was futile.
"I spoke frankly about the seriousness of this issue and quite frankly was astonished that this could have happened," Mr Thierens wrote.