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194 CLASSIFICATIONS OF OIL AND GAS ACCUMULATIONS

Fig. 10.11. Generalized performance of a closed combination-drive pool produced without control.
(Courtesy of E.C. Babson.)

gravity drainage is normally more critical than in the case of strict gravity-drainage
reservoirs because of a reduced tendency for downward oil migration. The gener-
alized performance of a closed combination-drive pool produced without control is
presented in Fig. 10.11. A good example of this type of reservoir is the Golden Spike
Field in Alberta, Canada.

10.4. CLASSIFICATION OF HYDROCARBON ACCUMULATIONS BASED ON THE TYPES OF
TRAPS
Although the classifications based on the form, type and genesis of oil and gas
accumulations are called the ‘‘hydrocarbon accumulation classifications’’ they are in
effect the trap classifications. These trap classifications may be grouped into three
major types and four subtypes.
I. Traps formed by folding (with or without faults). Accumulations formed as
a result of folding are usually associated with the bedded reservoirs. The
complexity of structure (sometimes even isometric), size, and especially height
are caused by the trap and reservoir position in the sedimentary basin. Over the