Seismic Survey

Surface seismic and vertical seismic profiling.

• Surface Seismic
  • Low cost
  • Better 3D coverage
  • Rarely used for DAS (Receiver sensitivity, for it’s only sensitive along the fiber. )
• VSP
  • One-way attenuation
  • Less depth/time uncertainty
  • Better coverage around the well

Helical cable for vertical sensitivity

• Not 3 component receiver
• Increase sensitivity to high angle wave.

Advantages for DAS in VSP

It has much higher accuracy and a higher range for it has a much higher density than geophone.

Different types of VSP

Includes zero offset, offset. walk-away, cross-well, reverse and deviated borehole.

4D DAS VSP

It enables us to monitor the structure. The source and receiver should be the same or very similar, and the fiber could be installed in the place permanently.

Case: Offshore

DAS is much more cheaper than 4D OBN, and it has a similar result compared with 4D OBN.

Case: Unconventional hydraulic frac

The 4D measurement should be applied every few weeks other than every few years. So It’s necessary to use DAS. They use 2 fiber to monitor the frac.