Vertical seismic profile

In geophysics, vertical seismic profile (VSP) is a technique of seismic measurements used for correlation with surface seismic data. The defining characteristic of a VSP (of which there are many types) is that either the energy source, or the detectors (or sometimes both) are in a borehole. In the most common type of VSP, Hydrophones, or more often geophones or accelerometers, in the borehole record reflected seismic energy originating from a seismic source at the surface.
There are numerous methods for acquiring a vertical seismic profile (VSP). Zero-offset VSPs (A) have sources close to the wellbore directly above receivers. Offset VSPs (B) have sources some distance from the receivers in the wellbore. Walkaway VSPs (C) feature a source that is moved to progressively farther offset and receivers held in a fixed location. Walk-above VSPs (D) accommodate the recording geometry of a deviated well, having each receiver in a different lateral position and the source directly above the receiver. Salt-proximity VSPs (E) are reflection surveys to help define a salt-sediment interface near a wellbore by using a source on top of a salt dome away from the drilling rig. Drill-noise VSPs (F), also known as seismic-while-drilling (SWD) VSPs, use the noise of the drill bit as the source and receivers laid out along the ground. Multi-offset VSPs (G) involve a source some distance from numerous receivers in the wellbore.