The Guardian quotes University of Alabama petroleum geologist Philip Johnson: "It if went uncontrolled it could certainly leak for two years and certainly longer than that. [...] But he said the leak rate would fall sharply over time once the natural gas in the reservoir is exhausted. "That is the driving force," he said. "As soon as that is gone, it won't leak at any serious rate."Hayward's Figure May Be Too Low By Ten
That's assuming that the 50 million barrel figured that Hayward cited is accurate. Another academic specializing in the oil industry is dubious that Hayward's stat is true:
"I would assume that 500m barrels would be a more likely estimate," said Tadeusz Patzek, the chairman of the department of petroleum and geosystems engineering at the University of Texas at Austin. "I don't think you would be going after a 50m barrel reservoir so quickly. This is simply not enough oil to go after."
Normally I'd try to offer some additionally commentary, but just let that sink in. Two to four years at 50 million barrels at the damage is truly enormous; that from 500 million barrels is entirely incomprehensible.
Is this what we've come to? Is even a thousandth of a percent chance of this sort of thing happening again work the risk? No, no, and no again!