Classification basis

Exploring for Oil and Gas Traps
Series	Treatise in Petroleum Geology
Part	Traps, trap types, and the petroleum system
Chapter	Classification of exploration traps
Author	Richard R. Vincelette, Edward A. Beaumont, Norman H. Foster
Link	Web page
Store	AAPG Store

All classification schemes have a basis from which they are organized. Some are more organized and systematic than others. The basis used for classification depends on the purpose of the classification. The bases for this scheme are the geologic elements critical to finding similar traps.

Purpose

The main purpose of the proposed scheme is to help explorationists find more oil or gas traps. A well-constructed classification scheme for traps can serve other useful purposes:

• It provides a means whereby traps can be organized and cataloged in an orderly manner. Once properly organized, the various trap types can be analyzed and compared to one another to provide valuable information for the exploration and development of similar features.
• A good classification scheme provides standardized terminology that can be used in communicating information to others about oil and gas accumulations.

Considering other schemes

Several classification schemes were analyzed and, where appropriate, were used as a basis for setting up the proposed trap classification scheme. Of particular interest was the biological classification scheme used to catalog and describe plants and animals. First proposed by Aristotle and then expanded and improved by Linnaeus, this system has stood the test of time. Although competing schemes have been proposed and modifications to the scheme are the basis of ongoing debate, the scheme has provided a valuable method of organizing and studying organisms.

Basis for biological classification

The basis for the biological classification scheme is similarity of morphology (shape) and phylogeny (evolutionary history). In addition, the processes that led to these similarities are also used in biological classification. For example, one of the major differences between plants and animals is that animals are mobile and can search for food, whereas plants are fixed or rooted and rely on food to be brought to them.

Ranking classes of organisms

The biological classification scheme places organisms in seven ranked levels, going from general to specific:

1. Kingdom

2. Phylum

3. Class

4. Order

5. Family

6. Genus

7. Species

The species represents one certain type of organism, which, by definition, cannot interbreed with an organism of a different species. The largest or most general grouping is at the kingdom level, which Aristotle originally used to separate plants (plant kingdom) and animals (animal kingdom). Interestingly, Aristotle also identified a third kingdom—the mineral kingdom—in which hydrocarbon traps presumably belong.

Similarities of classifying traps and organisms

The use of shape and evolutionary history in the biological classification scheme provides a basis for the use of similar attributes in a trap classification scheme. We propose to utilize similarities in geometry, composition, and genesis as the basis for classifying traps. These similarities are really critical geological elements that can guide exploration. Unfortunately, using a scheme identical to that used in biology has limitations in trap classification, primarily because our trap “species” are prolific interbreeders. Trying to classify most traps would be like trying to classify an organism that is a cross between an elephant and a bee with an apple tree growing out of its head. The “treephantbee” might be difficult to classify in the standard biological classification. However, if a proper classification would enable us to locate a herd of treephantbees, and if honey were oil, we might become rich indeed!

See also

• Classification philosophy
• Trap
• Classifying traps
• Trap systems: structural, stratigraphic, and fluidic
• Trap classification levels

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