Patent ID: 6856912

Claim:
A method of removing irregularities caused by tube waves from seismic data obtained in a borehole seismic survey, using a first set of transducers (seismic receivers or sources) and a second set of transducers (seismic sources or receivers) and wherein at least the transducers of the first set are arranged in a borehole, which method comprises the steps of (a) obtaining a set of original seismic data p m (t,k), wherein the integer k refers to the k'th transducer of the first set of transducers and the integer m refers to the m'th transducer of the second set of transducers; (b) subjecting the original seismic data set to a time-shift based on an estimated tube wave velocity to align the tube waves in time so that a set of time-shifted data {tilde over (p)} m (t,k) is obtained; (c) applying a filter to the time-shifted seismic data set {tilde over (p)} m (t,k) to obtain a set of time-shifted, predicted tube wave data {tilde over (q)} m (t,k); (d) undoing the time shift for the time-shifted, predicted tube wave data set {tilde over (q)} m (t,k) to obtain a set of predicted tube wave data q m (t,k); (e) subtracting the predicted tube wave data set q m (t,k) from the original seismic data set p m (t,k) to obtain a set of corrected seismic data p c m (t,k), and the original seismic data set by the corrected seismic data set; (f) subjecting the set of corrected, original seismic data to a time-shift based on a tube wave velocity opposite to the velocity used in step (b) to align the tube waves in time so that a set of time-shifted data {tilde over (p)} m (t,k) is obtained; and (g) repeating steps (c), (d) and (e) to obtain a set of seismic data of which irregularities caused by tube waves have been removed, characterized in that the filter applied in step (c) is a structurally oriented edge-preserving filter.