Creating S-Wave Images and S Attributes from Legacy P-Wave Data Acquired with Vertical Geophones
Bob Hardage, Senior Research Scientist, BEG UT Austin
The Exploration Geophysics Laboratory (EGL) at the Bureau of Economic Geology has developed technology that allows S-wave images and S attributes to be extracted from seismic data generated by common vertical-displacement sources (i.e. P-wave sources). The S mode used in these applications is not a P-to-SV converted mode but is a direct-SV mode produced exactly at the point where a P source applies its vertical displacement to the earth.
If P-source data are recorded with 3C geophones, the direct-P and direct-SV illuminating wavefields embedded in the data allow full-elastic imaging of all possible P and S modes to be done. If P-source data are acquired with only vertical geophones, then only two images can be made. One image is the usual P-P image that is produced by the downgoing illuminating P wavefield. The second image is a SV-P (converted-P) image produced by the downgoing illuminating SV wavefield.
SV-P data provide the same image and the same S attributes as P-SV data, the latter data now being used by several exploration companies. An important advantage of constructing S images and S attributes from vertical-geophone data is that this S-wave information is lying dormant in 1000’s of square miles of legacy P-wave data residing in seismic data libraries. By applying this EGL technology to legacy P-wave data, operators can engage in S-wave reflection seismology without having to record new data.
This presentation will illustrate the physics involved in direct-P and direct-SV illumination by common P-wave sources and show real-data examples of S-wave reflection seismology being applied across exploration prospects with P-wave sources.
Bob A. Hardage received a PhD in physics from Oklahoma State University. He worked at Phillips Petroleum for 23 years followed by management positions at WesternAtlas. He then established a multicomponent seismic research laboratory at the Bureau of Economic Geology where he is now Senior Research Scientist. He has been a member of SEG for 49 years and an AAPG member for 45 years. He has served SEG as assistant editor, editor, first vice president, president-elect, president, past-president, chair of technical program committee for two annual meetings, honorary lecturer, and short course instructor. SEG has awarded Bob a special commendation, life membership, and honorary membership. He wrote the monthly Geophysical Corner column for AAPG’s Explorer magazine for six years. AAPG has honored Bob with a distinguished service award for promoting geophysics among the geologic community.