Common-depth-point method for determining and displaying the shear-velocity reflectivities of a geologic formation

摘要

A novel method for determining and displaying the shear-velocity reflectivities of geologic formations is disclosed wherein a compression-wave common-depth-point seismic-data-gathering technique is utilized to produce both normal incidence compressional-velocity reflectivity sections and shear-velocity reflectivity sections for reflection points in given geologic formations. The subject method includes the gathering of common-depth-point information for a plurality of incidence angles, (theta) and estimating the linear coefficients (Rpp,0 and Rpp,1) of a linear function fitted to the amplitudes vs. sin2 (theta) measured for each point of reflection. The common-depth-point gather is conducted at angles of offset of less than 20-30 degrees such that assumptions concerning various elastic parameters: density, compressional wave velocity and shear-wave-velocity can be made which allow the application of linear fitting techniques to the gathered data. The sum of these coefficients corresponds to the shear-velocity reflectivity of the reflection point and may be presented with similar data for other points in appropriate shear-reflectivity sections.