Exploration Geophysics
Michael S. Bahorich

The evolution of two books published by the Society of Exploration Geophysicists (SEG) dramatically illustrates the enormous growth of knowledge in applied geophysics in recent years.

The fourth edition of SEG's all-time best seller, the Encyclopedic Dictionary of Applied Geophysics, appeared in 2002. It is 45 pages longer than the third edition, initially published in 1991, and the additional pages are definitions of new technical terms. Most pages have at least 15 definitions, so a conservative estimate is that today's competent applied geophysicist must know at least 675 more terms — and the nuances and (often considerable) mathematical complexities that accompany them — than the competent geophysicist of 1991.

SEG's number two all-time best seller, Seismic Data Analysis, has been a standard reference since its initial publication in 1987. That edition had 526 pages. The first revised edition, published in 2001, exceeded 2000 pages!

Those numbers leave no doubt that the 1990s were a time of major advances in applied geophysics. That decade will undoubtedly be best remembered as the one in which 3-D seismic became the basic tool for petroleum exploration and development because it dramatically improved the image of the subsurface. This improvement has been, quite justifiably, regarded as a breakthrough technology. Another advance of great important is the geophysical workstation. Originally developed to efficiently view 3-D data, the workstations allow multidisciplinary teams to integrate disparate data sets, prestack time and depth migration and time-lapse reservoir monitoring (often called 4-D seismic because it incorporates the fourth dimension, time).

Other advances of great importance — and this is hardly a complete list — were the adoption of the geophysical workstation (originally developed to efficiently view 3-D data) by multidisciplinary teams to integrate disparate data sets. Other advances are prestack time and depth migration, and time-lapse reservoir monitoring (often called 4D seismic).

The above is not even a complete list. At the same time, a cursory tour of the exhibition floor and technical presentations at SEG's 2002 annual meeting last October quickly convinces that the coming decade will produce additional breakthroughs. Those that I think most promising include:

Again, the above is a partial list, little more than a sightseeing tour of the exhibition floor at SEG's 2002 Annual Meeting (an which an excess of 250 companies had booths). It is possible, indeed the percentages might be favorable, that another technology on display in 2003 will have even more impact in the coming years.
I close with some thoughts that technology is bringing several areas of the earth sciences closer together. Deep Earth studies have historically been academic, while those applying geology to mineral exploration and environmental and engineering applications have focused their tools closer to the surface. The deep earth (earthquake) people use very low frequency data, the petroleum exploration people use slightly higher, and the near-surface folks use very high frequencies. What was noise to one group was meaningful to the other. But these groups are now beginning to use each other's data and techniques.

For example, the March issue of The Leading Edge, SEG's monthly publication, had a special section on "Solid-Earth Seismology." September will have one on "Ground-Penetrating Radar." These technologies have always operated in subsurface areas too deep or too shallow for practical use by the majority of applied geophysicists who work in petroleum exploration and development. However, as indicated by publication of these special sections, the areas are merging. Perhaps the current decade will be remembered as the one in which all geoscientists — deep Earth, mineral explorationists and near-surface engineering and environmental specialists — were able to take advantage of the benefits of both high- and low-frequency data.

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Bahorich works with the Apache Corporation in Houston.

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