by gego » Fri 15 Dec 2006, 23:17:10
$this->bbcode_second_pass_quote('EnergyUnlimited', 'T')his is one of better threads on this forum.
Nevertheless I think that this rapid fall of EROEI within last 15 years or so has much to do with wider use of "enchanced recovery technologies", which became very popular lately.
It is quite likely, that further EROEI drop will no longer be so fast, as current EROEI=3 already addressed this "technofixes" in oil recovery.
Shortly, I expect halving of current EROEI within next 20 years and not faster than that.
At high EROEI ratios, the energy used to acquire oil is hardly noticeable. At low ratios, the energy used becomes significant. The path from high to low is not a straight line.
In order to determine how much of gross energy is left after energy used at different EROEI ratios I used this formula:
1 - (1/EROEI)
For example, at an EROEI ratio of 50:1 it works out:
1 - (1/50) =.98 or 98% of the oil produced is available for humanity after energy used in getting gross oil.
Here is a little table using a starting value of 100:1 as per the data provided earlier in this thread, except instead of using the exact data I used a halving period of 20 years for the EROEI rate (which matched the earlier data except for the questionable drop to 3% in 2010).
100 EROEI = 99%
50 EROEI = 98%
25 EROEI = 96%
12.5 EROEI = 92%
6.25 EROEI = 84%
3.125 EROEI = 68%
1.5625 EROEI = 36%
.78125 EROEI = -28%
No wonder nobody worried (or even noticed) about cost of acquiring oil at those oil high EROEI ratios. It confirms the cancerous effect of progressively lower returns. Again, these numbers look at only the energy cost of getting oil, not the production levels. If this halving of EROEI every 20 years continues, then you can see from the above table how horrible would be the consequences of a falling EROEI ratio, and then you need to apply the applicable percentage to reducing production to see how many actual barrels are left to use. Of course it is not possible to go below 1:1 for any length of time.