Geoscience Reference
In-Depth Information
Fig. 2.37
Example of wavelet estimation by matching data to wells. The wavelet may be estimated
by deriving a matching operator between the seismic data and the well log predicted reflectivity. To
do this a small area of traces centred on the well location is examined and the match between each
trace and the well log is calculated. The best match trace is determined and the wavelet is estimated
together with the synthetic that is predicted using the wavelet and log derived reflectivity. Several
QC parameters are also given, the most important being the signal to noise estimate. The bottom
left-hand display shows the signal to noise plot for traces around a well; high signal to noise is
shown in blue. In this case we have a very good match with a signal to noise ratio of over 4 that is
obtained from a trace very close to the actual well location. The display on the right shows the
synthetic in white overlain on the recorded seismic data.
With luck, hard work and appropriate testing and parameter selection the result of
the complete processing sequence should be a section that resembles a cross-section
of the reflectivity through the earth with optimised seismic resolution and signal to
noise ratio. In practice it often takes several passes through the processing sequence
before this goal is satisfactorily achieved. Each pass through the data uses lessons learnt
from the previous processing route so that the next iteration may spend more time on
velocity analysis or multiple attenuation or use a different migration strategy. There
is also a different requirement from the data as we move from exploration through
