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 1

Figure 2 shows a zero or near offset VSP (left panel) and a corridor stack of VSP traces (right panel). The VSP has been corrected to two-way time so that reflections from horizontal reflectors appear at the same time on traces recorded at different levels. The corridor stack (right) is a partial summation or stacking of the VSP traces (left). Stacking, a summing of data to produce a single output trace, enhances the signal to noise ratio of seismic data.