Volume 35, Issue 2 (March 2012)
A Small, Lightweight Borehole Receiver for Crosshole and Downhole Seismic Testing
Crosshole and downhole seismic testing have traditionally employed the use of a downhole receiver consisting of geophones in a sealed container along with a separate inflatable bladder for seating the geophones against the inside of the boring. This configuration has been used with success, but these receivers can be relatively large and heavy. As an alternative, a smaller, lighter borehole receiver design has been developed. The prototype tool is approximately 19 cm (7.5 in.) long and 6.4 cm (2.5 in.) in diameter, and it weighs less than 0.68 kg (1.5 lb). The new design is a single pressuremeter-like unit in which small accelerometers are glued to the inside of an inflatable membrane. When inflated, the accelerometers are pressed against the borehole wall or casing, and excellent coupling is achieved. Typical results from field testing indicate that the new tool produces reliable results.