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Thursday, February 12, 2009

USA Field Size Distribution Update

I asked for some help in fleshing out some points on this reservoir field size distribution.

USA Field Size Distribution

A few days ago David N kindly sent me a copy of the Baker paper, and I transcribed some of the data points here.

The Baker paper collected statistics up to 1986, and consisted of data from about 14,000 fields. Robelius with more recent data put it at 34,500 fields.

From the data, it looks like between 1986 and now that many more of the smaller fields became developed and therefore got counted in the statistics. So in the last 20 years, we probably have gained substantial mileage from the low volume reservoirs, explained by either of these possibilities:
  1. Smaller fields get deferred for production due to economic reasons
  2. Smaller fields have a smaller cross-section for discovery so therefore show up later in the historical process. This second-order effect plays a smaller role in dispersive discovery than one would intuit -- i.e. not as if all big fields get found first, instead the probability weighting has a slight bias toward bigger fields.
Since 1986, I eyeballed the breakpoint at around 20 million-barrel fields. But now, if we try to generate a new transition breakpoint for the next 20 years, it would appear at less than 1 MB (C=0.6) as suggested by the dispersive aggregation model. This gets us close to physical limits and a real point of diminishing returns (but you probably knew that already).


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