Porosity Advisor--Expert System Used as Aid in Interpreting Origin of Porosity in Carbonate Rocks

W. Lynn Watney, James Anderson, Jan-Chung Wong

Porosity Advisor was developed to assist in interpreting the origin of porosity in carbonate rocks and to evaluate inexpensive rule-based expert-system shells in solving practical geological problems. The shells are programs that facilitate development of a knowledge base and an inference program to link rules and draw conclusions. The knowledge base consists of fact and rules. The facts include pore types and their relationships to matrix and cement. The rules relate these facts and, in turn, are used to make conclusions about the genesis of the pores. The genetic classification of P. Choquette and L. Pray is utilized to draw conclusions regarding process, direction, and timing of porosity development.

The facts and rules of Porosity Advisor are derived from studies of Upper Pennsylvanian carbonate rocks in the Mid-Continent. Particular facts in this data base include type of pores, crosscutting relationships, geochemical parameters, association with megascopic, mappable features, and burial history.

Facts and rules have different levels of significance because of imprecise measurement of facts and nonuniqueness of fact-rule relationships. Accordingly, confidence levels can be applied to both facts and rules. Some expert-system shells can read facts and rules from spreadsheet programs such as Lotus 1-2-3 and permit processing of large data sets. Programming options and tools such as these greatly facilitate the application and utility of these programs.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.