GEOPHYSICAL CORNER Part 1

This month's column, the first of a two-part series, is titled "The Check Shot Velocity Survey: Is It Enough?"

The Geophysical Corner is a regular column in the EXPLORER, produced cooperatively by the AAPG Geophysical Integration and SEG Interpretation committees, and edited by M. Ray Thomasson.

VSP Is a Check Shot Step Up

By R.J. BREWER

Graphics courtesy of R. J. Brewer

Figure 2

Figure 1 shows a typical equipment setup and seismic ray paths in a borehole seismic survey. In a checkshot velocity survey, only the first directly arriving signals sensed by the downhole geophone are used. In vertical seismic profiling, both directly arriving and reflected signals are used.