Application of an Expert System to Exploration Studies in San Juan Basin, New Mexico and Colorado

Betty M. Miller

The U. S. Geological Survey is currently exploring the feasibility of applying expert systems technology to three-dimensional basin analysis. This undertaking involves the development of a working prototype knowledge base that captures both the logic used by basin experts to define the geologic concepts needed for a basin analysis and the reasoning required to model the geologic evolution of a sedimentary basin as aids to assessing the basin's energy resources. This expert system, designed to analyzed the traditional concepts of source, reservoir, and trapping mechanism, aids in the diagnosis of geological conditions favorable for the occurrence of petroleum and other energy resources.

The knowledge base developed for the pilot study of this expert system centers on the San Juan basin and includes both surface and subsurface data sets that establish a three-dimensional perspective of the basin's fundamental stratigraphic and structural framework.

The San Juan basin, a 13,500-mi² Laramide structural basin in northwestern New Mexico and southwestern Colorado, encompasses a maximum of over 15,000 ft of Paleozoic to Eocene sedimentary rock and contains economic deposits of natural gas, oil, coal, and uranium. Successful exploration in this basin requires an understanding of the complex stratigraphy and structural geology controlling the distribution of these resources.

Expert systems techniques incorporated in this basin study to combine complex geologic and geophysical data are used to (1) develop knowledge bases that document the basic geology and geologic concepts that characterize a basin; (2) provide a diagnostic tool to aid in the geologic interpretation of the basin and to predict the favorability of occurrence of energy resources on the basis of the basin's geologic history; (3) provide an "intelligent" data management system for data base queries; and (4) interface geographic information system (GIS) digital mapping techniques for interpreting and manipulating spatial data bases with basin analysis techniques using expert systems for assessing the basin's resource potential.

A report on the work in progress covers the design and construction of the knowledge base for the San Juan basin. It includes geologic data bases, compiled from the Petroleum Information Well History Control System and other sources, for the Upper Cretaceous oil and gas-producing formations (the Pictured Cliffs Sandstone, the Gallup and Dakota Sandstones, and the Mesaverde Group). A two-component GIS, called ARC/INFO, enables the user to integrate and manipulate multivariate spatial data for geologic maps such as structure-contour, isopach, and facies maps for the major producing horizons in the basin. A demonstration prototype expert system for the basin was developed by using KEYSTONE, an integrated software package that provides a comprehensive expert system environment.

Expert systems technology provides the geologist with new tools for innovative research in geologic interpretation, for compiling and updating information data bases, for developing new concepts in basin analysis, and for applications to new resource appraisal methods.

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