The oil industry has entered into a new economic regime. It used to be how can I maximize how many dollars can I make this quarter, whereas in the last couple years, it's turned into how can I most efficiently make the most amount of dollars from all the oil that's still left. That's why they're making record profits, ironically enough -- they used to reinvest some amount of income as refineries, new drilling operations, capital outlays that would accelerate the extraction. Now there's no point to that, so instead they just keep the cash (EE I think described it pretty aptly as "the party at the end of the world.")
I wouldn't automatically assume that a sharp drop in their willingness to spend money accelerating extraction, means a sharp collapse in the amount of oil or the difficulty getting it from the ground. They're just abruptly adjusting their incentives, without necessarily a sharp jump in the physical-oil reality (just a continuation of the steady downward slide.)