EXPERIMENTAL STUDIES ON DOWNHOLE SEISMIC SOURCES

We have investigated various candidate downhole sources for reversed vertical seismic profiling and crosshole seismology. The potential sources studied included explosive charges, a perforating gun, an air gun, and a water gun. The studies were conducted in both open and cased holes in various lithologies. We found that an explosive charge or an air gun can be a viable direct source in both open and cased wells. However, the long-spaced sonic logging tool indicated that both sources may cause a deterioration of the cement bond between the formation and the casing where the cement is new and its integrity is questionable. -from Authors