By Janet Raloff, Science News
Crews responsible for drilling BP’s Macondo well in the Gulf of Mexico, this past spring, missed plenty of signs that a catastrophic accident was looming, according to a November 17 interim report by the National Academy of Engineering and National Research Council.
If heeded, those warnings should have afforded crews ample opportunity to head off an explosion aboard the floating Deepwater Horizon drilling platform, says Donald Winter, who chaired the panel that wrote the report. Winter, a former Secretary of the Navy, now teaches engineering practice at the University of Michigan’s department of naval architecture and marine engineering.
The team of experts that he headed uncovered errors in the tactics employed to complete the exploration phase of drilling.
Ordinarily, crews tap a well, check its potential to supply reliable quantities of oil, then put a temporary cap on it for a period that the industry refers to as “temporary abandonment.” Hibernation might be a more apt term
Explains Winter, the time between a well’s exploratory and production phases can run months. And with costs of leasing a drilling platform running perhaps $1 million a day, companies have an incentive to put a well to sleep until it can begin delivering crude.
It was during the final stages of preparation for this temporary abandonment that the April 20 explosion occurred, he notes. Minutes after displacing mud at the bottom of the well with seawater, crude oil began inappropriately climbing up the bore hole. For the next 50 minutes, this appeared to go unnoticed. Once crew members aboard the Deepwater Horizon did realize what was going on, Winter says, they tried to stop it. But their actions “were incremental; they were not very aggressive in terms of their attempts to control the flow.”
Once it reached the surface, the oil and gas ignited—killing 11 workers and destroying the drilling rig. The blowout would go on to massively fou the Gulf with more than 5 million barrels (more than 200 million gallons) of oil.
The new report found evidence that failures occurred during the cementing of the well that may have caused fractures—and an inability to seal the well from oil in the reservoir. Although there were apparently signs that something had gone wrong, workers either ignored or misinterpreted them, the report finds.
Not only was cement that was sent into the well casing not displacing an equivalent amount of drilling mud—thereby pointing to a potential leak—but there also were anomalous conditions present during cementing operations, which constituted additional hints that the cement might not be making the desired seal.
Winter’s panel also turned up evidence of poor training of crews—and/or their distraction during pivotal decisionmaking steps in the days and hours leading up to the accident.
For instance, the new report notes that several activities were underway as oil had begun snaking its way up from the reservoir, about five miles below the sea’s surface. The report charges that focusing on these activities—such as transferring drilling fluids to a nearby vessel—might explain why crews missed that intrusion of explosive hydrocarbons.
Cost cutting may have played a role
At a briefing on the new report, Winter and some of his coauthors were asked whether they had turned up evidence of a rush to that “abandonment” phase in order to trim drilling costs. The simple answer: Yes.
The panel focused on key decisions made aboard the Deepwater Horizon as preparation for the Macondo well’s abandonment was underway. “We’ve identified a number of these that we believe potentially contributed to the blowout,” Winter said at the briefing.
And in reviewing those actions, he said, it appeared that the crew failed to adequately appreciate the potential risks associated with the steps they were taking.
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Roger Cane 6:07PM November 18, 2010