if you put this in a graph then we would have a gradual downward slope with a sudden cliff at some point as I noticed in a news story about Alaskan production going to zero at 50% of current rate due to pipe pressure being too small. We could sort of generalize this as a metaphor that the spot markets,e tc. and finacial systme need a minimum pressure to work for the Exxons and NOC s to get the whole tanker and refineries and car manufacturers etc. profitabl so at a certain point a petroleum based economy loses economy of scale and collapses perhaps at 30% of current production so it just shuts down so we lose the last 30% of prodcution suddenly for all intents and purposes. This would mean effectively 700 billion barrels left with a normal looking decline curve suddenly going to zero in ten to 15 years out except for very local uses in primitive and old equipment.