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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 51 (1967)

Issue: 7. (July)

First Page: 1202

Last Page: 1224

Title: Current Uses of Computers by Exploration Geologists

Author(s): J. M. Forgotson, Jr. (2), C. F. Iglehart (2)


The six types of computer applications discussed herein are typical of those currently being used by geologists as an aid in solving exploration problems.

Industry-supported well data systems provide large volumes of scout-type data on punched cards or magnetic tape. These data can be filed, sorted, and retrieved rapidly to fulfill specified requirements. The computer also is used to handle large technical data files of individual companies. For example, micropaleontological and paleoenvironmental data from several thousand wells in the Gulf Coast area are stored on magnetic tape and retrieved by suitable programs, for the preparation of isopachous and paleogeographic maps.

Correlative electric-log markers or formation tops are recorded on punched cards or magnetic tape to allow rapid preparation of structural and isopachous maps using the computer in combination with automatic plotting equipment. Current programs have the option to restore to the figures on isopachous maps the thickness of the sections removed by normal faults. Maps can be prepared to indicate fault patterns, structural data, isopachous values, and isoliths of sandstones and combinations of sandstones. Truncation, onlap, shale-out, and other stratigraphic features coded by the geologist on the input data forms are indicated on printed results and plotted maps to aid in contouring and interpretation. The results of these computations are available in a format suitable for further applica ions such as automatic contouring and trend analysis.

Programs are available to prepare facies maps from quantified descriptive lithologic information. This use of the computer provides a rapid and economical method of performing the calculations required for a large variety of maps using various combinations of end members. These maps are helpful to interpret paleogeography, depositional environments, and trends favorable for the presence of porosity and hydrocarbon accumulations.

Computers are necessary for more complex types of statistical analysis, such as factor analysis. By this technique, large numbers of variables can be grouped or clustered into a smaller number of factors, each representing a combination of related variables or samples. Samples thus grouped into classes or factors have a certain degree of similarity and are used to define and map facies.

Trend analysis is a statistical technique requiring the use of the computer to separate observed quantitative data into a regional component and a residual component. This technique has proved useful in the interpretation of isopachous and structure maps based on subsurface data, seismic maps, gravity maps, and magnetic maps.

Computer programs designed to calculate the gravity effect of a known or postulated structure are useful for interpretation of deep salt-mass configurations. Models of assumed structures can be constructed from seismic or subsurface data and modified until the computed gravity agrees with observed gravity, thus indicating that the final model is a close approximation of the true structural conditions.

Computers will become more important in exploration as the ability improves to use them efficiently. The computer is a versatile and powerful tool to aid the geologist in data acquisition, data analysis, and data display, and should not be considered as a competitor. Experienced geologists should become involved in the development and evaluation of appropriate computer applications to provide necessary guidance in the development of useful applications commensurate with the high standards of the geology profession.

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