1965 Paper II-D

SUPPLEMENTARY COMPUTER PROGRAMS FOR DIPMETER ANALYSIS

By

Robert R. Matthews - Continental Oil Company, Ponca City, Oklahoma Tom D. Mooney - Continental Oil Company, Midland, Texas Robert B. Haynie - Continental Oil Company, Midland, Texas James C. Albright - Continental Oil Company, Ponca City, Oklahoma

ABSTRACT

Field recorded digital magnetic tapes of dipmeter well logs have been available since 1961. Primary processing of these tapes by a high speed digital computer usually gives many closely spaced correlations. We have found it useful to perform certain additional processing of these data in order to simplify the job of interpretation of the dipmeter log.

Four computer programs have been written to perform this supplementary processing. The first is simply a plot of dip versus depth on a regular (5 inches = 100 feet) logging scale. The dips are plotted as a letter indicating the quality of the correlation with an arrow pointing in the direction of dip. A second program calculates and plots (on a foot-by-foot basis) the average dip and the amount of data scattering in each depth increment. To use the third program, we first divide the well into intervals, using the results of the first two programs. The program then plots all dips within an interval on a single plot with polar coordinates. The dips are plotted as a letter indicating quality. The angular position of the letter shows the azimuth of the dip, while the distance from the outside circle is the dip angle. A single grouping of points indicates a consistent dip through the interval, while multiple groupings may indicate cross-bedding or a fracture pattern having a different "dip angle" from the basic bedding planes. The fourth program prepares a cross-section plot which shows how the computed dip results cut across a vertical plane through the wellbore. The vertical plane may be oriented in any desired direction. These programs are set up to use all computed dips or to ignore selected dips discriminated against on the basis of quality, hole size, or dip range (i.e., only dips between a preset maximum and minimum are used).

Field examples are included which show the usefulness and versatility of these programs in the interpretation of dipmeter logs.