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')I agree with other posters that HL plots may not necessarily be good predictors of either future production or URR.
However, IMO, the HL plots are more likely to be too optimistic.
Let me illustrate this with an example of a fictional oil producing country called "Sudia".
In this example, Sudia is blessed with a fair amount of oil in a small number of super giant and giant, shallow oil fields. The initial estimates of these fields predicts a URR of about 170Gb.
Here is the complete graph of the 30 year history of Sudia Oil Production:
Here's what happened:
Initially, production was ramped up fairly quickly due to the shallow wells and initial high pressure in the fields.
By year 8 production has reached almost 6Gb/yr, but pressures are dropping and by year 10 production appears to be plateauing.
At this point the Sudians discover water injecion and the pressure in the fields is maintained. Production from smaller fields is added in the following years allowing production to grow to over 11Gb/yr in year 22.
All this time the oil columns in their super giant fields are getting smaller and smaller, but by managing the water injection carefully, the Sudians keep the production at what appear to be indestructible levels.
But in the 22nd year of production (when they are at their Peak), disaster strikes as most of the largest Sudian fields completely water out as their oil columns disappear.
Sudian oil production then collapses as only the very small fields are left, and by year 30 it's all over.
Now the HL plot of this entire production would look like this:
But let's assume we are only looking at the graph up to their peak in the 22nd year (Q=140Gb). The line I added to the graph would appear to fit the HL plot up to that point, and seems to predict a URR of 400Gb (which the Sudians themselves believe and publicly announce that their reserves have actually 'grown' to this new figure).
However, the sudden collapse of these fields means that the actual URR ends up being only 180Gb.
The trouble I have is that most of the 'mature' HL plots (ones that plot fields that have gone to completion) are based on production that has had only very late help from advanced EOR techniques. I believe that these techniques produce non-symmetrical production curves with sudden collapses. This is essentially what Matt Simmons in predicting.
If the bulk of the world oil supply is coming from fields that will exhibit this behaviour, then the world HL plot could be misleading us into thinking that we've still got a fair amount of oil to extract.
Anyway, I'd be interested in peoples thoughts on this. I'm going to bed now (3am), so I'll check back tomorrow.
