Introduction to this special section: Borehole geophysics

When borehole geophysics technologies and applications come to mind, often we think of vertical seismic profiles (VSPs), checkshots, or wireline logging measurements. Problems that have been addressed include resolution enhancement, coverage, illumination, and time-to-depth conversion, among others. The papers in this special section, however, extend these relatively well-known techniques to include salt proximity work, use of high-pressure and ultrahigh-pressure geophones in VSPs, distributed acoustic sensing (DAS), acoustic wellbore ranging, refinement of velocity models and image enhancement, and impacts on business value. Although all the papers could have been about, for example, DAS or vertical resolution improvements, this special section turned out to be broader in terms of the application of borehole geophysics. What drives the need for borehole geophysics in these applications? Is it the significance of business value? Is it scientific and engineering knowledge? Is it some combination thereof? The answers to those questions are not addressed directly, but each paper is unique and offers useful results and techniques across many disciplines. This special section is not extensive in terms of the number of papers, but those included are well worth reading.