VSP Re-processing & Field Studies

Reprocessing of VSP data sets can be useful for a number of reasons; for example you may want to:

• Create a digital data set for old well(s) where currently only paper data are available.

• Use modern processing techniques to achieve an improved result.

• Investigate a new zone of interest for example a deeper target.

• Pursue additional processing options to extract additional information and/or parameters not considered at time of the original processing. 

• Establish trends in key parameters which requires uniform reporting and digital output on a field wide basis.

Survey Type Well Trajectory  No. of Geophones / Separation P-wave Processing Options S-wave Processing Options
  P T-D P Log Calibration 1D P- Reflection Profile 2D/3D            P-Image Q Anisotropy AVO Wavelet Maching S T-D S Log Calibration 1D S- Reflection Profile 2D            S-Image 3D            S-Image
Rig Checkshot Vertical 10-30 Variable                      
Rig Checkshot Deviated 10-30 Variable ✓**                      
VI Checkshot Deviated 10-30 Variable ✓** ✓**                      
Rig VSP Vertical 30-300 at 10 to 25m ✓*     ✓* ✓* ✓* ✓*  
Rig VSP Deviated 30-300 at 10 to 25m ✓** ✓** Along Wellpath ✓**     ✓** ✓** ✓** Along Wellpath* ✓*  
VI VSP Deviated 30-300 at 10 to 25m ✓** ✓** Along Wellpath ✓**     ✓** ✓** ✓** Along Wellpath* ✓*  
Offset VSP Vertical 30-300 at 10 to 25m                     ✓*  
Offset VSP Deviated*** 30-300 at 10 to 25m       ✓**               ✓**  
Walkaway VSP Vertical 12-32 at 10-25m         ✓** ✓**         ✓*  
Walkaway VSP Deviated 12-32 at 10-25m       ✓**   ✓** ✓**         ✓**  
3D VSP   12-100 at 10-25m ✓✓   ✓* ✓* ✓* ✓* ✓* ✓* ✓*
*   Results not guaranteed
** The technique has limitations which need to be understood at the design stage

Field studies cover not only the processing of all the borehole seismic data from a single field but also these data can be used to assist the processing and interpretation of surface seismic data to provide a high resolution and consistent result in both time and depth. In general a field study would aim to achieve the following:

  1. Match seismic data to borehole data across the field.
  2. Establish the relationship between time and depth at formation tops then use this information to calculate average, RMS and interval velocity to the tops for all wells.
  3. Incorporate the time depth and interval velocity profiles, which will indicate trends or inconsistencies, into surface seismic derived models.
  4. Establish other key parameters at the well location such as rate of high frequency absorption (Q), changes in lithology giving rise to mode conversion, measured shear wave velocity profile from mode converted wave. Calculate rock property information like Youngs modulus.
  5. Identify time or depth zones that are affected by interbed multiple activity. Potentially, use the VSP to clarify the principle multiple generating horizons.
  6. Use VSP data and parameters derived from the VSP to help suppress problems with multiples in the surface seismic.
  7. Derive operators at each well to match the VSP which is known to be zero phase, to surface seismic data. 
  8. Interpolate results between wells and extrapolate to edge of field, where practical.

Re-processing projects will always have specific goals and we are always happy to discuss these and most important to assess the suitability of the available data to address the problems posed.

Remember to undertake re-processing it is not always necessary to have digital data. Often we can start from paper field records or a stacked file and paper log data. We can also handle a variety of digital formats.

Feel free to contact us if you need more information.