Wave equation modeling

Wave equation modeling of water layer multiples can be achieved by downward continuation of shot records followed by adaptive matching of the multiple model to the input record.

Multiple estimation is done with F-K extrapolation and removal of the estimated water-related multiples is done by a 3-component method on a trace-by-trace basis.  Each multiple trace is analyzed for an optimum overall time shift, amplitude factor and phase angle to convert it into the original shot trace.  The factors are then applied to the multiple trace prior to subtraction from the original.  

Success is dependent on the degree of seabed dip which is not comprehended.

 

Radon Filter

TGS Imaging routinely uses Radon Filtering techniques to attenuate multiples. Normally the multiples are modeled and subsequently subtracted from the input seismic trace data. The Radon Analysis tool is used to transform the data to Time-Moveout space (‘p’ space) so that a suitable mute can be picked to eliminate the primary energy. The remaining multiple energy is then subtracted from the input data.

Our technique uses a two-pass approach to give better attenuation. In the first pass the CDP gathers are NMO’d using water velocity and the water bottom multiples are removed. Later in the processing sequence, and after initial velocity analyses have been run, a second pass of Radon is applied. Here the gathers are corrected with primary velocity and the radon mute picked as above to enable subtraction of remaining multiple energy.

The example shows a CDP gather after 1st and 2nd passes of Radon have been applied.