A Wax-Coupled Borehole Seismic Detector for High-Resolution Measurementsby Thomas E. Owen, Southwest Research Inst, San Antonio, United States,
Jorge O. Parra, Southwest Research Inst, San Antonio, United States,
Abstract: A triaxial borehole seismic detector was developed for high-resolution measurements at frequencies up to 2,000 Hz. Applications for this detector include three-component shallow reverse vertical seismic profiling, shallow reflection surveys, and interwell velocity logging and imaging. A meltable wax embedding technique was developed to provide rigid conformal detector planting at the bottom of shallow boreholes with the advantage that the detector is recoverable after use. Wax coupling provides a stress-free plant which conforms to the borehole to give excellent broadband three-component response at frequencies up to 2,000 Hz; a frequency range largely unexplored for seismic applications. A second version of the detector was devised to provide pneumatic wall-lock coupling for practical use in the field. Comparison tests revealed that both designs are effective three-axis seismic detectors at frequencies up to 1,500 Hz and that the wax-coupled detector has near-ideal response at frequencies up to about 2,500 Hz. The wax-embedded detector is an ideal reference sensor and the preferred sensor for applications requiring maximum seismic signal fidelity at high frequencies. The pneumatically coupled detector is a practical prototype high-resolution probe for high-quality three-component measurements at frequencies up to about 1,500 Hz.
Subject Headings: Probe instruments | Seismic tests | Boring | Seismic design | Seismic surveys | Coupling | Seismic effects | Imaging techniques
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