Combination of fragile geological structure and a flawed seismic survey in Chevron oil spill

After an oil sheen trail about a kilometer long was discovered on Friday, March 16, in the same area of the Frade oil field, in the Campos Basin, off the coast of the state of Rio de Janeiro, where Chevron Brasil had a 2,400 barrel oil spill last November, specialists became seriously worried about more oil spills.

Specialists are pretty much in agreement on three points. First, as professor Moacyr Duarte of the Federal University of Rio de Janeiro (Coppe/UFRJ) says, Chevron’s seismic survey should have shown them that the area was fragile. After the first oil spill in November, Chevron pumped concrete into the well under pressure, “not a good idea in a weak geological structure,” he points out. Adalberto da Silva of the Geological Department at the Fluminense Federal University says, there was “an error in perforation operations.” Silva complains that there is very little information from Chevron, but says it seems clear that old cracks in the seabed opened due to high levels of pressure used in drilling or in plugging the November oil spill or both. Third, Segen Estefen, director of Innovation and Technology at Coppe/UFRJ, says that one result of what Duarte and Silva have pointed out is that there could be a progressive collapse of the seabed above the petroleum reserve. And that could result in chronic leaks through small cracks over a very large area making control difficult.

David Zee, an oceanographer, describes the situation as “…an accident was caused by the perforation. That triggered a chain reaction in a fragile seabed. You are dealing with a structural flaw that is geological. As soon as you have any oil spill, no matter how small, you will have environmental impacts.”

Professor Duarte concludes by saying that the vast so-called “pre-sal” (that is, located below a layer of salt) oil reserves recently discovered off the coast of Brazil in ultra-deep water, runs through a zone of geological instability. “Drilling in that environment will require highly sophisticated studies and technology, not to mention constant monitoring. Robots with cameras will probably be needed. Surveys that have already been made will have to revised in light of what we have just learned. This is urgent.”