Multicomponent seismic reflection profiling ? some scale model experiments

Abstract

Reflection experiments have been carried out on simple two-dimensional laboratory models to demonstrate the advantages of multicomponent profiling over conventional scalar wavefield recording. The 2 ´ 2 matrix of observations were taken with a biaxial piezoelectric receiver (vertical and horizontal receivers) and two piezoelectric source types ? vertical force (P wave) and horizontal force (S wave) ? to record the complete vector wavefield. The four component data were processed using a controlled direction reception (CDR) filter, which transforms the data into four sections for interpretation: PP, PS, SP and SS, including all mode conversions. In these sections not only is the specified linearly polarised wave type enhanced but coherent noise such as Rayleigh waves (elliptic polarisation) and incoherent background noise (isotropically polarised) is suppressed. With a single component source and a single component receiver, recording and interpretation of the various wavefields is difficult. Using vector wavefield recording and processing, it is easy to separate and identify compressional-wave reflections, shear-wave reflections, and all mode converted waves (PS reflections and SP reflections). The availability of S wave sections, in addition to conventional P wave sections, lends new insight to seismic interpretation. It improves the accuracy in prediction/seismic mapping and yields better vertical and horizontal resolution of the structure. In addition, the multicomponent sections contain diagnostic information on lithology, porosity, fluid content and anisotropy of the medium.