Each day, another way to define worst-case for oil spill

Even the most sober analysts are quick to say that this is such an unpredictable well that almost anything is possible. Bruce Bullock, director of the Maguire Energy Institute at Southern Methodist University, said additional leaks are a possible source of deep-sea plumes of oil detected by research vessels. But this part of the gulf is pocked with natural seeps, he noted. Conceivably the drilling of the well, and/or the subsequent blowout, could have affected the seeps, he said.

"Once you started disturbing the underground geology, you may have made one of those seeps even worse," he said.