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Wednesday, December 06, 2006

USA N.G. (Not Good)

I recently posted a model of USA natural gas production based on discovery data of Laherrere. This model assumed a constant depletion rate over time and fit the real production curve in scale only. I prefaced use of the model with the caveat that natural gas reservoirs may not necessarily deplete at a rate proportional to the amount left, which forms the underpinnings of the oil shock model. I imagine that a natural gas reservoir might deplete closer to an analogous water cooler, maintaining a steady flow until empty -- which conversely also means that one can throttle the rate presumably just as easily.

As the shock model does allow a variation of extraction rate over time, I decided to fit the production curve again, but this time letting the extraction rate vary all over the place.

As a first step I adjusted the (fallow,construction,maturation) rates down to 0.1 (10 year 1/e time) from the previous 0.133 to match the early evolution of the curve. Combining the static rates with the variable extraction rates I generated the following fit and error curve.

Remember that this pertains to conventional sources of natural gas; de Sousa covers the distinction between conventional and unconventional in a TOD post, but this goes in more detail. Other than that, it looks like we have started to squeeze the blood out of the proverbial turnip. I really think the increase in extraction rate comes from improvements in technology allowing us to more than maintain the flow in the face of increases in demand. Sucking out 10% per year of the volume worked fine for us for the better part of last century, but as we hit the 80% (!) level, hard constraints have to follow. And that means we will soon see the steep cliff typical of natural gas depletion. Why don't any of the news organizations talk about this? Do the energy companies figure that we will go quietly, whistling past the graveyard as these conventional sources of NG disappear? (pause for rhetorical interlude)

And remember the helium shortage during the recent Thanksgiving holiday? Guess where helium comes from? Certainly not unconventional sources of natural gas. Oh yeah .. reservoirs containing conventional natural gas. Double gulp. Not good.

Bye-bye toy balloons, hello bulbous LNG tankers.

Update: On reviewing my only other natural gas model, New Zealand NG shows the same characteristic upswing in extraction rate on nearing a cliff. Note that USA extraction rate more than doubles in a similar time frame.


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