Geostuff manufactures rollalong switches and wall-lock borehole
geophones, accessories for seismic surveys.
A borhole geophone is a particular type of vibration detector for seismic waves--one that is designed to be used in a hole drilled in the ground. A wall-lock geophone is one designed to clamp the phone against the side of the borehole wall, usually so that S-waves or shear waves can be recorded. For more information, visit the Borehole Geophone section below.
A Rollalong Switch is used in exploration seismology to select a group of geophones from a longer array placed on the ground surface. In common mid-point (or CMP, or common depth point, or CDP) reflection surveys, the geophone array is moved a short distance each shot. It is more convenient to do this electrically with a rollalong switch. For descriptions, visit the Rollalong Switch section below.
Geostuff Wall-Lock Borehole Geophones
Geostuff offers a selection of wall-lock borehole geophones. Model BHG-2 (pictured on the right in photograph) contains a 3-component geophone in an X-Y-Z orientation. The outside diameter is 1.85 inches (47 mm), small enough to fit inside a schedule-40, 2-inch plastic pipe. The clamping mechanism is a robust, steel spring compressed by a DC electric motor.There are no rubber bladders to break or tubes to leak, and operation is relatively independent of depth. BHG-2 models have been used to depths of 500 meters (consult factory for details). Geophone elements are available with 10, 14, 28 or 40 Hz natural frequencies.
This unit is also available as the BHG-2C with
a flux-gate compass which will indicate the orientation of the geophone in the
hole (except for steel-cased holes). Interest is growing in horizontal
anisotrophy as awareness of the problem increases.
The BHG-3 (pictured, center) includes both a fluxgate compass and a servo
mechanism which automatically rotates the horizontal geophones to the azimuth of
your choice. Simply point the compass (located in the lower cylinder) towards
magnetic north, then orient the clamp spring toward the desired direction
The BHGC-1 Controller is available. This unit switches power to the clamp
mechanism and compass, and also directs the geophones to selected seismograph
channels.
The clamping mechanism is operated by a DC motor, actuated by power sent down
two of the conductors. The polarity is reversed to release the clamp. A
controller is relatively easy to construct and a schematic is provided in the
instruction manual for those who wish to build their own.
The cable is a 7-conductor copperweld with Kevlar braid and polyurethane jacket,
specially manufactured by Tescorp Seismic Products.
A
Reed Products SU-8F waterproof connector is molded on the wet end and a Cannon
NK-27-21C on the dry end. The cable can be easily disconnected from the geophone
for ease of handling. Extension cables are also available with a pair of male
and female connectors, so that the cable can be temporarily lengthened for
unusually deep holes.
The standard clamp mechanism works for
holes between 2 and 6 inches (48-150 mm), but for large holes the Big Hole Kit
is available (below). This mechanism easily installs in place of the standard
spring on any of the BHG series and will expand up to 19 inches (48 cm).
For more information please contact Red Dog Scientific Services
Geostuff is the world's leading manufacturer of rollalong switches. Models are available for a wide range of exploration seismographs with from 24 to 144 channels. The 24 and 48-channel systems are particularly well suited for shallow reflection surveys for engineering, mining and environmental seismic surveys, by virtue of their light weight and compact size. A variety of adaptor cables are available to mate with any commercial seismograph.
The smallest unit is the RS-96/24 (pictured on right). This is a 24-channel rollalong switch which can accept inputs from up to 96 geophones. It is supplied with an output cable with dual NK-27-21C connectors (pictured) which will mate with most standard 24-channel seismographs.
The RS-120/48 (pictured, center) is used with 48-channel seismographs and accepts inputs from up to 120 geophones. The unit has an adjustable gap between channels 24 and 25. Adaptor cables are available.
The RS-264/144 (pictured, upper left) provides up to 264 inputs and 144-channel output for petroleum reflection surveys.
For more information please contact Red Dog Scientific Services