Intro
 It involves recording seismic energy from wells (not just from the
ground surface)
 Benefits:
- Higher vertical resolution
- Less near-surface effects
 Drawbacks:
- Expensive
- Only covers near-well area
- Low spatial resolution (the wells are far away from each other)
Types
 Sonic Logs (Acoustic well logging)
 Uphole and Downhole Surveys
 Check Shot Surveys
 Vertical Seismic Profile (VSP)
Sonic Logs (Acoustic well logging)
 The instrument is called sonde.
 The sonde is lowered down the well, and
records continuously.
 It is used to calculate formations velocity by
measuring the time needed for a sound wave to
travel a specific distance in the formation.
Sonic Logs (Acoustic well logging)
Uphole and Downhole Surveys
 Uphole: seismic sources are in the borehole and the receiver on surface.
 Downhole: seismic receivers are in the borehole and the sourse on
surface.
 Used in shallow wells.
 The objective: to calculate the thickness and velocity of the weathering
layer (which is a layer at or near the surface, possibly unconsolidated
and has air-filled pores, where seismic velocities are substantially low).
Uphole survey
Downhole survey
Check Shot Surveys
 It is done by recording of first arrivals along a deep well.
 The objective: to calculate the thickness and velocity of the
subsurface layers.
Check Shot Surveys
Vertical Seismic Profile (VSP)
 https://wiki.seg.org/wiki/Borehole_geophysics