Abstract Where two or more reflections are more closely spaced than a quarter wavelength, a common situation for stratigraphic features of interest in petroleum exploration, the same half-cycles of the embedded wavelet tend to add; we call this the “thin-bed” case. In contrast, where they are close but separated by more than a quarter wavelength, different half-cycles tend to add; this is the “thick-bed” case. Many characteristics of seismic reflections differ in thinand thick-bed situations. On unmigrated seismic sections the limits of horizontal resolvability are imposed by Fresnel-zone considerations. However, on migrated sections other factors become important, such as noise on the unmigrated section, spatial aliasing, migration aperture, and uncertainties imposed by velocity, stacking, and two-dimensional assumptions.

Abstract Improvements in seismic data acquisition and processing techniques make it possible to observe geologically significant information in seismic records which has not been evident in the past. New types of measurements help in locating and analyzing geologic features, including some hydrocarbon accumulations. Analysis of a seismic trace as a component of an analytic signal permits the transformation to polar coordinates and the measurement of quantities called “reflection strength” and “ instantaneous phase.” These, plus several other quantities derived from them, are called attribute measurements and can be coded by color on seismic sections. Such color displays permit an interpreter to associate measurements and changes in measurements with structural and other features in the seismic data. They thus facilitate identification of interrelations among measurements. A series of examples shows how such analysis and display helps in locating and understanding faults, unconformities, pinchouts, prograding deposition, seismic sequence boundaries, hydrocarbon accumulations, and Stratigraphic and other variations which might be misinterpreted as hydrocarbon accumulations.

Abstract The “Glossary of Terms Used in Geophysical Exploration” published in Geophysics in February 1968 met with some justified criticism because of the emphasis on seismic exploration for oil. The Addendum published in April 1969 attempted to restore balance as far as mineral exploration was concerned. But one major area of geophysics had still been slighted: that of well logging. This present addendum is intended to complete our coverage of geophysical exploration terms. Well logging technology has seen rapid development in the last few years with the advent of several types of acoustic and radioactive logging methods and other new logging tools. Computers are beginning to have an impact on this field by making readily available, from combinations of logs, information which previously could be extracted only by tedious methods. The author believes that a “geophysicist” should be conversant with aspects peripheral to his central COncern and central application, and that a geophysical interpretation ought to be consistent with all available data of all kinds, not merely with that portion of the data in which the interpreter specializes. Sonic logging information is vital to seismic interpretation and density logging information to gravity interpretation. But vital also are measurements of other physical properties with which an interpretation ought to be consistent, just as a seismic interpretation ought to be consistent with gravity and magnetic observations. In a rapidly changing field such as ours, the boundaries between areas of specialization must be crossed more and more often as we advance into the future. Hence it seems appropriate

Abstract “This text presents explanations and definitions of many terms currently and previously used in well logging.”