October 31, 1975 - Gerald R. Ford Presidential Library and Museum

Two of these fields are quite complicated geologically. The
operators did not discuss interpretative or proprietary information with
the consultant firm. The FEA study reports are extremely brief and
generally undocumented. In the absence of additional data, a choice
cannot be made as to which estimate best reflects actual reserves.
In the case of a third fie1d study, the volumetric data were based
upon very old published infonnation. The operator quite possibly has
more recent and more re 1tab 1 e data and i nterpretat ion s •
In the case of a fourth field, an instance of questionable
methodology in the field study could account for the difference between
the two proved reserves estimates.
The last field report was prepared in considerably less time than
the other studies. Therefore, this report cannot be subjected to a
critical revie\t.
These last five fields are Cai110u Island, Cogdell, Hastings,
Oregon Basin, and West Cote Blanche Bay.
Natural Gas Proved Reserves. A short discussion of the 34 instances in
which natural gas reserves from the Operators Survey and the Major Field
Studies differ by more than 20 percent follows:
1. In sixteen of the gas fields in the "high percentage difference"
category, the proved reserves differences, regardless of percent, were
low in absolute amount. The recorded differences were each less than
90 BCF, and in thirteen instances, 45 BCF or less. By way of comparison,
the average proved gas reserves for 58 fields (excluding Prudhoe Bay
and Hugoton) are about 415 BCF for the studied fields and about 528 BCF
for the surveyed fields.
2. Possible explanations for the proved reserves differences in
seven fields are apparent from review of the field studies. Proved
reserves data for six of these fields are listed in Table 12.
Table 12--COMPARISON OF NATURAL GAS PROVED RESERVES
Operators Survey Field Study
Field (BCF) (BCF)
Altamont 388 40
Brown Bassett 341 203
Carthage 345 465
East Texas 364 226
San Juan - Basin Dakota 2,807 2,064
San Juan - Blanco 6,458 3,358
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