VSP Vertical Seismic Profile shows a geophone measurements at different depths in the well which are sent to receptors on the surface. When the source is at a considerable horizontal distance of the well head, the result is an offset VSP.

For Azimuth VSP offsets exist in different directions. In a walkaway VSP source geophone moves while stationary. In a reverse VSP the source is in the hole and surface geophones.

The VSP vertical seismic profile can be made both for directional and horizontal wells. A VSP walkabove is performed with the probe in a deviated hole and placed vertically above the source. The result is a VSP corridor We often presented in a stack.

The first step is usually a correction of the slant-path propagation time because that is not vertical raypath. The depth z of the probe divided by the time the first break tv gives the average velocity V (z) and Z exchange between change of TV gives the velocity range Vi. The energy coming rapidly after TV is used to perform a corridor stack also called Outside corridor stack. If Tv (z) is deducted for every stroke, arrivals are acentudas. If the source generates S-waves and a 3-component geophone is used, the wave arrival can be seen and if their travel times are added to each stroke, the reflection of S-waves can be seen clearly.

LIST OF VERTICAL SEISMIC PROFILES

OBJECTIVE – ACQUISITION REQUIRED

* Improved speed analysis – Zero Offset VSP
* Correlation surface / pit – Zero Offset VSP
* Increased resolution in depth – Zero Offset VSP
* Time-depth conversion – Zero Offset VSP
* Calibration to register – Zero Offset VSP
* Identification of the primary reflector – Zero Offset VSP
* Analysis of multiple masters – Zero Offset VSP
* Identifying Seismic lithology – Zero Offset VSP
* Operator deconvolution – Zero Offset VSP
* Improving information poor area – Zero Offset, Offset VSP
* Overcome data area – all types
* Estimated porosity – Zero Offset VSP
* 2-D stratigraphic Image – Offset VSP, deviated well survey
* 2-D structural image – Walkaway VSP, offset VSP, deviated well survey.
* Estimates of depth – Zero Offset VSP
* Estimates strike – Multiple Offset VSP or deviated well survey
* Delineation of salt dome flank – Proximity survey, Offset VSP
* Location of top of salt – Zero Offset VSP, offset VSP
* Location of the interface granite / sediment – Zero Offset, walkaway VSP, offset VSP
* Analysis of S and P waves – Zero Offset P / S VSP, Offset P / S VSP, 3-component geophone
* Analysis of seismic attenuation – Zero offset, offset VSP
* Amplitude versus Offset – Offset Walkaway
* Secondary recovery – all types
* CT Studies – Multiple wells, downhole survey / geophone surveys
* Studies of permeability – Tube wave VSP
* Movement of particles / polarization studies – Offset VSP, 3-component geophone
* Orientation of fracture – Shear wave VSP, offset VSP, 3-component geophone