Downhole / Crosshole

Dowhole and Crosshole are seismic techniques to measure wave’s propagation velocity in wells, with higher precision and resolution compared to surface recordings.
The Downhole registry consists in a tri-axial geophone lowered into a well while seismic waves are generated on surface. At specific depths, the geophone records directly the waves transmission times.
The Crosshole utilizes two wells, one to generate the seismic waves and the other to register the wave’s transmission times from one to the other.