There are basically two major unknown factors in the depletion modeling problem:
- the URR which fluctuates between 1,800 Gb (ASPO) and 4,000 Gb (USGS)
- the world depletion rate which is expected to be between 1% and 5%
I assume the following:
- a geometric demand growth (+2%)
- a geometric depletion with different rates (1% to 5%);
Consequently, instead of assuming a particular curve model like in the Hubbert approach, I applied two exponential curves (EIA approach): A geometric demand growth prior to peak and a geometric depletion post-peak.
For each value of the URR and for each depletion rate, I compute the fraction of oil extracted before the peak (blue curves) and the year of the peak (red curves). The fraction of oil extracted indicates the degree of asymmetry of the curve (50% means a symmetric curve i.e. production midpoint= PO). The curve can be used as following: you fix your URR and you obtain a range of possible PO dates corresponding to different depletion rates. The blue curve will give you the degree of asymmetry.
![Image](http://photos22.flickr.com/25739507_2c9bc0f3f8_o.png)
The ASPO estimate give the most symmetric production curve. For a given URR, a higher depletion rate will push the PO date (technology improvements).