Model-based removal of water-layer multiple reflections

We have developed a procedure to attenuate water-layer multiple reflections . We estimate the sea-bottom reflectivity function and use it plus calculat ed amplitude functions to model all order water-layer multiple reflections, taking into account both amplitude and waveform shape. We model the primar y and multiple reflections from the sea bottom in the frequency-slowness do main. The amplitude function in the data modeling includes the source direc tivity function, source ghost response, receiver array directivity function , receiver ghost response, and offset-dependent geometrical spreading. For small offsets we can assume that the seabed reflectivity depends only on fr equency, and it is estimated using a least-squares algorithm. An unknown sc aling constant in the data is estimated using the amplitude of the primary and first multiple reflection from the sea bed. The composite sea-bottom re flectivity is estimated as a function of frequency for each common midpoint (CMP) position. We apply the algorithm to high-resolution seismic data fr om the North Sea. The modelled data match the recorded data well: and the estimated primary reflectivity is more geologically meaningful than the stacked trace. By com parison with Radon transform multiple removal applied to the same data, the model-based method was more computationally efficient and left less residu al multiple energy.