Several days prior to the Deepwater Horizon oil rig explosion, BP used a cheaper, riskier method to seal off the oil well, according to a New York Times report. The approach taken by the company was described as the “best economic case†in a BP document provided to the Times by a Congressional investigator.
The type of casing BP chose for Deepwater Horizon could allow gases from the well to leak as far as the wellhead, where only a single seal would serve as a barrier. The alternative would have provided two barriers.
While more expensive initially, the type of casing BP ultimately chose would be cheaper and more versatile in the long-term. But such a casing could also cause problems if drilling mud or cement is lost or pushed away from the well into porous rocks as it is pumped, the Times said. Apparently, that did happen several times, including once in March when the rig lost all of its drilling mud, and again just a few days before the April 20 blast.
A Wall Street Journal report published today is also shining light on some key decisions made by BP officials aboard Deepwater Horizon that may have contributed to the disaster. For instance, they cut short a procedure involving drilling fluid that is designed to detect gas in the well and remove it before it becomes a problem. They also skipped a quality test of the cement around the pipe, despite signs of problems with the cement job and a warning from cement contractor Halliburton Co.
Both of these decisions meant that rising gas had an easier path up and out of the well, the Journal said. Then, the day of the explosion, it was decided to proceed with removing heavy drilling fluid known as “mud,” despite results of a critical negative pressure test that BP officials have conceded was a an “indicator of a very large abnormality.†According to a Congressional memo released yesterday, BP officials have since said the decision to continue work may have been “a fundamental mistakeâ€.
The Journal is also reporting that there was a “skirmish” between TransOcean workers and BP officials on the rig the day of the explosion. TransOcean owned and operated the rig, and leased it to BP. Apparently, TransOcean officials disagreed with a decision by BP’s top manager about how to remove drilling mud and replace it with lighter seawater before sealing it with a cement plug. Removing the mud keeps it from polluting the sea but also means there’s less weight to hold down any gas, the Journal said.
After the mud was removed, BP was supposed to install a giant spring to lock the seal at the top of the well that would have helped prevent leakage in the event that gas was coming up the sides of the well, pushing against the seal. However, the Journal said there is no indication in the rig’s activity logs that the spring was ever installed.
BP also opted to remove the mud before placing a final cement plug inside the well. That left little to prevent any gas inside the pipe from rising to the rig, the Journal said.
Finally, the BP official overseeing the final well test did not have much experience with deep water drilling, the Journal said. He told congressional investigators that he was aboard to “learn about deep water.”
According to the Journal, some of BP’s choices allowed it to minimize costly delays. Work on the well was behind schedule. According to a company document seen by the Journal, BP approved spending $96.2 million and about 78 days on the well. The target time was much less—about 51 days. By April 20, the well was in its 80th day due to delays.
A technician who operated underwater robots and worked for a subcontractor on the rig told the Journal that he thought too many jobs were being done at once.
