Multiple attenuation in the CMP domain
We have observed many types of multiples on shot gathers in worldwide assortment of shot records. Multiples are attenuated based on two principle criteria — periodicity and velocity discrimination. As in the case of coherent linear noise, these criteria are exploited in whichever domain they are applicable. For instance, periodicity is preserved to a great extent for short-period multiples and reverberations on CMP gathers, especially at near offsets. Periodicity also is preserved in the τ − p domain, provided multiples are associated with near-horizontal reflectors.
CMP stacking facilitates attenuation of multiples based on velocity discrimination between primaries and multiples. This criterion to attenuate multiples also can be exploited in the f − k, τ − p, and Radon-transform domains. The degree of success depends on the moveout difference between primaries and multiples, and hence, on velocities and arrival times of primary reflections, and the cable length. Specifically, the moveout difference between primaries and multiples decreases at shallow times, low velocities, and at near offsets.
- Introduction to noise and multiple attenuation
- Frequency-wavenumber filtering
- The slant-stack transform
- The radon transform
- Linear uncorrelated noise attenuation
- Multichannel filtering techniques for noise and multiple attenuation