Converted-wave seismic exploration: An update

Robert R. Stewart

Multicomponent seismic recording (measurement with vertical- and horizontal-component geophones and possibly a hydrophone or microphone) captures the seismic wavefield more completely than conventional single-element techniques. Multicomponent surveying has developed rapidly, allowing creation of converted-wave or P-S images. P-S imaging uses downgoing P waves that convert on reflection, only at their deepest point of penetration, to upcoming S waves. Current P-S sections are approaching (and in some cases exceeding) the quality of conventional P-P seismic data. The advancements in multicomponent seismic acquisition, processing, and interpretation techniques have led to a number of applications for converted-wave surveys. Uses that have arisen include structural imaging (e.g., "seeing" through gas-bearing sediments; improved fault definition; enhanced near-surface resolution), lithologic estimation (e.g., sand versus shale content; porosity), anisotropy analysis (e.g., fracture density and orientation), subsurface fluid description, and reservoir monitoring.