Parameter Estimation and Fault Detection by Three‐component Seismic and Geoelectrical Surveys in a Coal Mine*

Abstract

BREITZKE, M., DRESEN, L., CSOKAS, J., GYULAI, A . and ORMOS, T. 1987, Parameter Estimation and Fault Detection by Three-Component Seismic and Geoelectrical Surveys in a Coal Mine, Geophysical Prospecting 35,832-863.Three-component seismic and geoelectrical in-mine surveys were carried out in Lyukobanya colliery near Miskolc, Hungary to determine the in situ petrophysical parameter distributions and to detect inhomogeneities in the coal seam. The seismic measurements comprise an underground vertical seismic profile, using body waves, and an in-seam seismic amplitude-depth distribution and transmission survey, using channel waves. The geoelectrical measurements are based on the drift-and seam-sounding method.Interval traveltime-, amplitude-, multiple-filter-and polarization analysis methods are applied to the seismic data. They lead to a five-layer model for the strata including the coal seam. The coal seam and two underlying beds act as a seismic waveguide. The layer sequence supports the propagation of both normal and leaky mode channel waves of the Love-and Rayleigh type. A calculation of the total reflected energy for each interface using Knott's energy coefficients shows that the velocity ranges of high reflection energy and of normal and leaky mode wavegroups coincide. The excitation of wavegroups strongly depends on the seismic source. A simultaneous inversion of a geoelectrical drift-and seam-sounding survey prevents misinterpretations of the seismic data by clearly identifying the low-velocity coal seam as a high-resistivity bed. Calculations of dispersion and sounding curves improve the resolution of the slowness and resistivity in each layer.Both diminished amplitudes and distortions in the polarization of transmission seismograms and decreasing resistivities in a geoelectrical pseudosection of the coal seam are related to an inhomogeneity. 8323-COMPONENT SEISMIC AND GEOELECTRICAL SURVEYS 833 A calculation of synthetic seismograms for Love and Rayleigh channel waves with the finite-difference and the Alekseev-Mikhailenko method agrees well with the field data for the main features, i.e., particular arrivals in the wave train, wavegroups, velocities and symmetries or asymmetries.This in-mine experiment demonstrates that the simultaneous acquisition, processing and interpretation of seismic and geoelectrical data improve the lithological interpretation of petrophysical parameter distributions. Coal seam inhomogeneities can also be detected more reliably by the two independent surveys than by one alone.

Using geophysical methods to define the attitude and extension of water-bearing strata in the Miocene sediments of the Pannonian Basin

“…Joint inversion of seismic and resistivity data has also been reported in the literature (Breitzke et al, 1987;Dobroka et al, 1991). However, even after combination of data sets, inherent ambiguities in the interpretation remain.…”

Seismogram Synthesis and Recompression of Dispersive In‐seam Seismic Multimode Data Using a Normal‐mode Superposition Approach

“…Only in the group-slowness range below the normal modes can the strong amplitude maximum of the P-and leaky-mode wave groups be distinguished between about 200 and 400 Hz and between 0.2 and 0.4 s/km (250&5000 m/s). As far as the resolution of the petrophysical parameters is concerned, the shearwave velocities and thicknesses of both coal-seams, C1 and C2, may vary by only about 20 m/s and 0.02 m respectively, as discussed by Breitzke et al (1987). The dirt-band parameters could be resolved to about 50 m/s and 0.2-0.3 m. The shearwave velocity of the host rock could only be evaluated approximately within a range of +_ 2W300 m/s.…”

A joint inversion algorithm to process geoelectric and surface wave seismic data. Part II: applications

“…The Schlumberger data were collected at 20 logarithmically equidistant points between 1.6 m and 125 m. The dipole-dipole measurements were taken at 20 logarithmically equidistant dipole positions between 2 m and 160 m, while the pole-pole data were recorded at 15 logarithmically equidistant points in the interval from 1 m to 25 m. The 2 Hz geoelectric transmitters and receivers were constructed at the Department of Geophysics of the University of Miskolc. These instruments are described in detail by Breitzke et al (1987). The apparent resistivities obtained by the Schlumberger, dipole-dipole and pole-pole arrays are shown in Fig.…”