Multi-offset VSP

In 15 years, VIBROMETRIC performed more than 200 VSP surveys for characterizing rock storage facilities and waste disposal sites.

The VIBROMETRIC Multi-Offset VSP method produces 3D maps of deep fracture zones, faults and lithological contacts. 

Fracture zones and faults of any orientation, including the steeply dipping, can be mapped at great depth.

The 3-component receivers placed deep in the bedrock record high resolution data for detailed fracture imaging.

 Measurements performed in several boreholes give a comprehensive image of the of fracture zones and faults at the scale of the whole site.

The rock features observed by VSP are subsequently correlated with borehole logs and hydrogeological observations.

There are three basic reasons why the VSP layout has been preferred to surface profiling for in-depth characterization of the bedrock:

1. With VSP-surveys, the source and the detectors can be placed in the bedrock itself, producing higher signal frequencies and thus better resolution in detecting thin features.

2. The fracture zones and faults in the bedrock can have any orientation and the dipping features are difficult to map in depth using surface reflection data.

3. VSP is, generally, a more economical solution than a 3D surface seismic survey.

At sites with a complex geology, the seismic velocities through different formations are estimated by tomographic inversion, using 3D ray tracing.

The velocity tomograms, here projected on a plane for easier visualization, indicate the velocity in the bedrock and in the overburden as well as the position.