f τ-p Domain processing of walkaway VSP data

Traditionally 3-component Walkaway VSP data U(x,t)z (acquired at different geophone levels (z) and with a line of source positions (x) crossing near the rig) are processed by first ordering the traces into successive Fixed Source gathers (U(x,t)z -> U(z,t)x). The gathers are next processed individually in order to enhance the primary reflected P wavefield followed by a recordering to the (x,t)z domain before migration. The main drawback in the processing scheme is that neither periodicity in the up- and downgoing multiples nor the possibility of efficient removal of unwanted shear events are present in the (z,t)x domain. In consequente the usefulness of Walkaway VSP data is regarded with some scepticism.