Three-Component Seismic Data: Researcher's Toy or Interpreter's Tool?
Deborah R. Miles, Gary S. Gassaway
Three-component seismic data have been recorded, analyzed, and studied by research groups for the last 10 years. However, the cost of acquisition and the difficulty in tying the P-wave reflections to the S-wave reflections have made three-component data nearly useless to the interpreter. Instead of solving interpretation problems, three-component data added a whole new set without providing any answers. These problems will be solved through the help of two recent developments: the three-component geophone with polarization filter (OMNIPHONE) and three-component amplitude-vs.-offset (AVO) analysis.
The OMNIPHONE can eliminate the need for geophone arrays by removing ground roll from the data without affecting the body waves. Waveform distortions caused by geophone arrays are attenuated, allowing for recovery of a greater bandwidth of signal. The OMNIPHONE also sends all three signal components to the recorder on a single channel in a format compatible with current field systems. The need for three channels per geophone station is thereby eliminated. Because three-component data can be recorded with fewer geophones and recording channels, field operations using OMNIPHONES are more efficient and less expensive than when using conventional three-component geophones.
Three-component (AVO) analysis can provide the interpreter with a tie between the P-wave, S-wave, and converted-wave reflections, as well as a means of calculating corresponding velocities. Current technology calls for stacking the S-wave data with the converted-wave data. However, AVO analysis identifies the S-wave and converted-wave portions of the radial gather, thus providing the processor with the information necessary to produce stacked S-wave and converted-wave sections of superior quality. Now the interpreter can look for anomalies in the P-wave and S-wave sections to predict changes in Poisson's ratio, which may in turn be used to determine lithology and pore fluid.
Other benefits of three-component seismic data include: increased structural resolution particularly in areas of complex geology, determination of subsurface anisotropy, three-dimensional filtering techniques for noise rejection, and improved time ties between seismic sections.
AAPG Search and Discovery Article #91035©1988 AAPG-SEPM-SEG Pacific Sections and SPWLA Annual Convention, Santa Barbara, California, 17-19 April 1988.