Comparison of high-resolution wax-embedded and pneumatically coupled borehole seismic detectors

Journal Article · Fri Jan 01 04:00:00 EST 1993 · Geophysics; (United States)

DOI:https://doi.org/10.1190/1.1443344· OSTI ID:6065396

Owen, T E; Parra, J O ^[1]

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1. Southwest Research Inst., San Antonio, TX (United States)

High quality seismic measurements at frequencies up to about 2,000 Hz are needed if projected resolution limits on the order of 1m in spatial dimension are to be realized in reservoir structure delineation, cross-well sonic logging, and shallow reverse VSP applications. While sources and detectors are critical to this goal, the authors have investigated detector requirements in an objective way to demonstrate a successful design philosophy capable of achieving unprecedented wide-band frequency response and data quality in three-component shallow-borehole sensors. Two prototype detectors were developed: a nearly ideal responding wax-embedded reference'' detector and a pneumatically coupled detector exhibiting closely comparable performance. Their approach uses a three-axis accelerometer sensor assembly installed in a borehole drilled through the weathered surface to a depth at which the ground is competent enough to support practical kilohertz wave propagation. The wax-coupled detector is planted using a meltable wax embedment to achieve a rigid, stress-free, conformal coupling at the bottom of the hole. Experimental test results show this wax-embedded detector to have excellent broadband three-component response at frequencies up to 2,500 Hz; a range heretofore unexplored for seismic applications. The pneumatically coupled detector, although limited by modal resonance distortion effects in the highest range of frequencies, demonstrated useful three-component response at frequencies up to 1,500 Hz. Tests of the two coupling techniques under identical conditions illustrate their high-quality responses and their differences. Field tests of the prototype pneumatically coupled detector in shallow reverse vertical seismic profiling (VSP) measurements demonstrate the practical effectiveness of the basic high-resolution probe design concepts.

• OSTI ID: 6065396
• Journal Information: Geophysics; (United States), Journal Name: Geophysics; (United States) Vol. 58:1; ISSN GPYSA7; ISSN 0016-8033
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
580000 -- Geosciences
ACCURACY
COMPARATIVE EVALUATIONS
DESIGN
EVALUATION
GEOLOGIC DEPOSITS
GEOPHYSICAL SURVEYS
MEASURING INSTRUMENTS
MINERAL RESOURCES
PERFORMANCE
PETROLEUM DEPOSITS
RESOLUTION
RESOURCES
SEISMIC ARRAYS
SEISMIC DETECTORS
SEISMIC SOURCES
SEISMIC SURVEYS
SURVEYS