Down/down deconvolution

Summary Images constructed from up-coming wavefields can be very effectively deconvolved using up/down deconvolution, however, they have geometry related drawbacks that reduce the quality of the shallower zones. In contrast, the down-going wavefield, which is imaged using mirror imaging, does not suffer from such geometry related disadvantages, however, it lacks a powerful deconvolution technique akin to up/down deconvolution. We use a modified Delft feedback model to describe the up- and down-going scattered wavefields. Using these results, we illustrate how up/down deconvolution works and then go on to introduce a new idea called down/down deconvolution. This new technique inverts the down-going wavefield for the Earth’s response in the absence of a free-surface. The free-surface multiples are removed and the 3D source wavefield is deconvolved to produce a result that is theoretically the same as up/down deconvolution. As a result we can combine the geometrical advantages of the down-going wavefield and the benefits of a powerful deconvolution technique. We illustrate this new idea using a synthetic dataset and a real 3D OBN dataset from the North Sea.