Page 169 - Petroleum Geology

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TABLE 7-3

North America’s ten largest oil fields in 1968 ranked according to ultimate recoverable
reserve estimates (from Moody et al., 1970, p. 17), with the estimates of the Zipf constant.
Figures in millions of barrels

Ultimate reserves Rank x ult. reserves
-
1 East Texas, Texas 5600 5600
2 Wilmington, California 2500 5000
3 Eunice-southward, New Mexico 2334 7002
4 Poza Rica, Mexico 2100 8400
5 Pembina, Canada 1773 8865
6 Kelly-Snyder, Texas 1683 10,098
7 Panhandle, Texas 1647 11,529
8 Swan Hills, Canada 1318 10,544
9 Elk Hills, California 1303 11,727
10 Golden Lane, Mexico 1205 12,050

and second columns, the Zipf constant being 12.3 X 10’ bbl of recoverable
oil.
The first result above is in reasonable agreement with the actual figures of
35%, or 46 X 10’ bbl, in the 45 largest fields, but the size predicted for
Rank 45 is little more than half the minimum size required for inclusion in
this group of 45 fields.
Moody et al. (1970, p. 17) list the North American giants of this group,
and Table 7-3 shows the top-ranking ten fields from this list with their esti-
mated ultimate recoverable reserves and each estimate of the Zipf constant
(reserves X rank number). Tables 7-2 and 7-3 show that the predictionsare
not very good, but they suggest that the East Texas field is not the largest
accumulation in North America, and that Wilmington may only rank 4th or
5th eventually.
Zipf’s law is also applied with yet another modification. The largest field
is taken as Rank 1; Rank 2 will have half Rank 1’s reserves, Rank 3, one third,
and so on. Table 7-4 shows the results of manipulations on this basis. The
results are not very convincing. This could be because Zipf‘s law does not
apply to North American (or any) oil fields, or because there were more giants
to be found that would rank amongst the ten largest.
In the event, Prudhoe Bay field (which, but for an event in recent history,
would be classified as a Russian oil field) had been found before the list of
Table 7-3 had been published in 1970, and its recoverable reserves were soon
to be estimated at 20 X 10’ bbl, later to be reduced to 9.6 X lo9 bbl- 70%
larger than the East Texas field. This was to be followed during the 1970s
with about 44 giants in North America (Fitzgerald, 1980), and when the ulti-
mate recoverable reserves of these can be fairly estimated, no doubt a new
table would look different again.