Exactly the small fields have complex economics if you will. For example under the current economic conditions small offshore fields probably won't be redeveloped with secondary gas/water injection once primary production declines. Stripper wells have their on economic pattern and contribute 2mbd to US production for example. In many cases decisions to not continue production or move to more extreme extraction measures in many fields means they won't be developed again in the near future. As and example a lot of the oil production in Texas is from fields that where capped back in the 1980's and not developed again until thirty years later.

I estimated using the WAG method :) that about 15% of the worlds oil production was in this high risk category.
This fits well with Kehbab's estimate of 30% of the worlds oil production coming from small fields. Some of the high risk oil is in larger fields on the edge of steeper declines so given that 15% seems to be a very good ballpark estimate.

The only positive is that we are probably not doing a very good job of counting the contribution of smaller fields to the worlds oil supply in the first places I'd not be surprised if we are not underestimating the contribution of these fields by several mbd say 2mbd or so. So we could very well not even see the decline in the official numbers for some time. The WAG method indicated we would enter steep decline in 2008 this is in rough agreement with Kehbab's more realistic results but I think both approaches suffer from using the official totals since they should start from some "real" production level thats probably higher then the official numbers or better simply outside of the official numbers.

What this means is official production numbers will probably be high for a while even though real production is falling rapidly. In fact you get a sort of strange result in that as smaller production fails more oil will be sourced from monitored production and storage resulting in even higher initial estimates of both the oil supply and the amount in storage. Whats happening is some small tank storage associated with some small fields is drained as the field declines and its being replaced with "official" storage thats actually counted coming from larger producers.

I wonder if Kehbab can come up with a guesstimate of the amount of oil thats both in this high risk group and also not in the official estimates this is oil we need to adjust for.

Also of course for the same reason we probably have consistently underestimated the contribution of smaller fields so we probably also underestimate how many are approaching steep decline. All of this will serve to make the initial fall from the decline of small fields difficult to predict since I believe that we are missing enough data to make the initial error on the same order of magnitude as the decline rate. I've got no idea if the various potential sources of error tend to cancel or not. So the big question is is there any systematic bias thats skewing results for small fields.

And fantastic work Kehbab ! I've been concerned about this for some time its great to see some real work done on the problem.

The international numbers don't make much sense to me. Baker-Hughes states that they do not have data for Russian or onshore China, however, they have zero for rigs in Iran and many other countries. The number of active rigs is considerably lower for the rest of the world when compared to U.S. and Canada. Maybe Rockman or somebody else can explain why that would be possible.