A microprocessor-based orientable three-component seismic sonde has been built and tested. The sonde is designed to share a single four-conductor logging cable with similar sondes via standard processor networking. Each sonde microprocessor receives serial communications from a wellhead computer, instructing it to measure the tilt and magnetic orientation of the sonde, accurately control a motor-driven pinning arm, collect, stack and store three-component gain-ranged seismic data at rates up to 3.6 kHz (1.2 kHz/channel), and transmit three-component full waveform seismic data uphole at 9600 baud using standard RS-232 components. The on-board tiltmeter permits the orientation of the sonde to be deduced if a borehole interval has a known oriented tilt vector. The sonde clamping mechanism is sufficiently strong to sustain cable tension in excess of 2250 N (500 lbf). A principal use of the sonde has been to acquire seismograms that resolve crystalline rock fracture-induced S-wave velocity anisotropy to ∼5 msec (Δt/t ∼ 3 to 5 per cent).

First Page Preview

First page PDF preview
You do not currently have access to this article.