Eric Von Lunen & Robert Barba, Schlumberger Well Services
Borehole sonic transit time measurements have been used by engineers and geologists in west Texas since the mid-1950's. The great majority of this sonic data has been acquired in open hole. With recent improvements in acquisition and processing technology, reasonable data can now be obtained in cased wellbores. The purpose of this study is to compare cased hole data with the established open hole data standard. The evidence suggests that usable compressional and shear transit time data can be obtained through casing. There are over 120,000 cased wellbores in west Texas as of this writing. A large percentage of these were surveyed prior to the development of most current petrophysical and geophysical processing techniques that require sonic inputs. With this technology, these wellbores can now be properly evaluated.