Shallow VSP work in the U.S. Appalachian coal basin

Abstract

Most geophysical applications in North American coal exploration have centered around the conventional surface seismic reflection method to provide continuous subsurface coverage for evaluating both good and anomalous coal reserve areas (Ruskey, 1981; Dobecki and Bartel, 1982; Greaves, 1984; Lawton, 1985; Lyatsky and Lawton, 1988; Gochioco and Cotten, 1989; Lawton and Lyatsky, 1989; Gochioco and Kelly, 1990; Gochioco, 1991; Henson and Sexton, 1991). The surface seismic reflection method, however, has inherent resolution limitations because the seismic wavelet must propagate substantial distances through the weathered layer, resulting in rapid attenuation of the desired higher frequencies. Since the depths and thicknesses of coal seams are usually known before‐hand, it is imperative that the seismic reflection associated with the target coal seam is absolutely identified in the seismic section to avoid misinterpretations. However, it is common that checkshot data and sonic and density logs are not available to generate synthetic seismograms to assist in the interpretation of coal seismic data. To overcome some of these limitations, the vertical seismic profiling (VSP) technique was tested in a coal exploration program to provide additional information for correlation with surface seismic reflection [or common‐depth‐point (CDP)] data and a synthetic seismogram generated from density and sonic logs.