Extending the seismic bandwidth — A simultaneous uncorrelated VSP and surface seismic field test study

A controlled simultaneous VSP and surface seismic field test was conducted to evaluate the evolution of the vibroseis chirp wavelet. We verify that the partitioning of seismic energy is independent of sweep rate for different sweep designs. We demonstrate under what conditions the seismic bandwidth can be extended using the semblanceweighted deterministic deconvolution process in the uncorrelated domain for zero-offset VSP, walk-away VSP, and simultaneous borehole and surface seismic data. The deterministic deconvolution process requires knowledge of the chirp wavelet in order to transfer the harmonic energy from the seismic noise domain into the seismic signal domain. Its performance depends on knowledge of the chirp signature and ambient noise. As expected, the ambient noise conditions in the well were extremely low as compared to the higher noise levels recorded in the surface seismic data. Under low ambient noise conditions, the semblance-weighted deconvolution can extend the recoverable bandwidth beyond the predefined pilot bandwidth for both the VSP and surface seismic data independently. The high level of surface ambient noise conditions in our field test limited the effectiveness of the VSP operators to extend the recoverable bandwidth of the surface seismic data.