Contrary to what’s been reported previously, a last-ditch effort to shut in BP’s blown-out oil well actually functioned as intended on the night of the deadly Deepwater Horizon rig explosion, but it ended up causing more destruction because of undetected bowing of a critical pipe, a new investigative report found.
The U.S. Chemical Safety Board released a comprehensive investigation report on the Deepwater Horizon explosion on Thursday, more than four years after the incident 50 miles from Venice, La., killed 11 workers and set off the worst offshore oil spill in U.S. history.
The independent government body was held up by fights with the rig owner, Transocean, over subpoenas for documents. Once the CSB got access to the information, it produced a report that makes few new discoveries overall, but does make key distinctions about exactly how highly technical mechanisms failed the night of April 20, 2010.
The report’s main focus was the Deepwater Horizon’s blowout preventer, the four-story stack of valves and pistons that sat at the bottom of the Gulf of Mexico, a mile below the rig, and stood as the last barrier between bubbling hydrocarbons and the ignition sources on the floating rig.
Other investigations -- by the Interior Department, Coast Guard, Congress and a presidential commission, among others -- found that a series of missteps taken individually may not have caused the blowout, but combined they proved catastrophic.
The CSB, however, kept its focus on the blowout preventer, or BOP.
"I think what you have here is a very narrow, very specialized look at one piece of equipment that they believe had more to do with the ultimate accident than everything else and all the other mistakes that might have been made," said Eric Smith, professor at Tulane's A.B. Freeman School of Business and associate director of the Tulane Energy Institute.
Previous reports could not definitively say if the final, last-ditch automated process of slicing the drilling pipe and closing in the blowout preventer actually worked on the night of the event. Some found the “blind shear rams” took two days to finally activate. But the CSB was able to get new data and run new tests to determine that it most likely did work the night of April 20.
A marine board investigation in 2010 and 2011 discovered the buckling of the drill pipe that was running down through a mile-long "riser" pipe, through the blowout preventer on the sea floor and into the well. But the CSB went further to try to explain why the pipe warped because of opposing pressures inside and outside of it. The warping was critical because even though the slicing rams activated, the bowed pipe was not in the right place to be properly cut and sealed.
The CSB found that another set of sealing valves actually did stop the flow of oil and gas briefly, but when a second explosion on the rig activated the automated slicing rams, the flow of oil was restored by the off-center cut.
“What these technical findings and conclusions mean for industry is that the buckling of drill pipe can actually occur when a well is successfully shut in by the drill crew and remain undetected," said Cheryl MacKenzie, investigative team leader for the CSB. "This means similar deficiencies identified in the Deepwater Horizon BOP could remain undetected in BOPs today. ”
The rig crew was confused by high-pressure readings on the pipe before the incident, but concluded that safety tests were a success anyway. That led to removal of counter-balancing drilling mud and without that slurry in the well and riser pipe, the oil and gas had a clear path to the surface.
The two BP rig leaders who made that conclusion have been charged with multiple counts of manslaughter by the federal government. But the CSB report indicates that BP and Transocean didn’t have a process in place for interpreting those test results and the “effective compression” that caused the bowing of the drill pipe was not well understood in the industry.
The timing of the report is intriguing because it comes as U.S. District Judge Carl Barbier is trying to decide if BP and silent parnter Anadarko, the owners of the well, should pay civil pollution fines for simple negligence or much higher fines for gross negligence. The difference between the two could be a whopping $15 billion.
The CSB report is silent on the issue of negligence, but its conclusions about the depth of the mechanical failures could have an impact. The level of mechanical failure exposed in the report is staggering -- not only the bowed pipe, the confusing test results and the dead batteries, but also an improperly wound solenoid coil that probably should have prevented the BOP's fail-safe slicing rams from working at all, except that a second error actually counteracted the first and allowed the "pinchers" to function.
The report also calls into question whether the federal government has implemented strong enough new safety regulations in response to the Deepwater Horizon incident. It praises the Bureau of Safety and Environmental Enforcement for implementing a new safety regime with new rules and tougher inspections, but the report said BSEE has not addressed the lingering weaknesses of blowout preventers or the need to properly test for such unforeseen impacts as the "effective compression" that bowed the Deepwater Horizon's drill pipe.