When one taps an oil reservoir the oil requires a certain amount of differential pressure to push it towards the well, and with the passages it must pass being generally narrow, flow is relatively constricted. Good well management means that, in order to control water and gas problems, the pressure difference between the well and the rock is carefully controlled, and this allows the oil to be effectively recovered at rates which, while worryingly increasing, are still generally considered to be less than 10%..
Natural gas, on the other hand, flows a lot more easily, and normally does not have a lot of the constraints that producing oil has. Thus, if your pipeline can handle the flow, and there is a demand, the gas field can be drained much more rapidly, with a consequent dramatically more rapid conclusion to the flow. As Dr Campbell pointed out fields may last just months, and then "boom" they are gone.
Adding this to the fact that North-America will soon have to import natural gas from other continents in the form of liquefied natural gas (LNG, natural gas liquefies at approximately minus 160 Celcius), that the price of natural gas are high and will certainly keep rising this winter, and the problems keep pilling up.
A sad eventual outcome would be for coal to displace natural gas when it starts to run out; things would only get worse. One more reason - as if we needed more - to invest massively in clean energy technologies such as wind, solar and hydro/wave.