OBN Clipping Correction for 4D Processing and Imaging

Up/Down Deconvolution (UDD) is valuable in the field of time-lapse (4D) seismic imaging in a marine environment, as it recovers Earth’s reflectivity free from changeable factors such as water column variability and source variability. UDD is very sensitive to the accuracy of the recorded water wave, however. In shallow marine environments such as the North Sea, the high amplitude of the water wave, due to the proximity of the source to the receiver, means it can overload the dynamic range of the recording equipment causing a clipped waveform. Clipping of the water wave creates severe artifacts on the reflectivity produced by UDD. Existing solutions to correct for clipping of the water wave are not robust enough under the scrutiny of 4D imaging when using UDD. Here, we describe a new wavefield filtering method for correcting clipped energy by predicting replacement values from coincident geophone data. In our example from the Valhall life-of-field 4D seismic dataset, the new method outperforms the common industry practice of wavelet replacement. Results suggest this method is robust enough to recover errors of the water wave recording, and it can be used to achieve consistency between up and downgoing wavefields.