Removing irregularities from seismic data caused by tube waves
AssigneeShell Oil Company
InventorsGijsbert Christiaan Fehmers, William Alexander Mulder, Rene-Edouard Andre Michel Plessix
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Abstract
Method of removing irregularities caused by tube waves from seismic data obtained in a borehole seismic survey, using a set of seismic or sources and a set of seismic receivers each arranged in a borehole, in which seismic data is time shifted based on an estimated tube wave velocity, filtered and then the time shift is reversed and applied to the original data set resulting in a corrected set, which is again time shifted opposite to the original time shift to remove and identify tube wave irregularities.
Claims20
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 pm(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 qm(t,k);
- (e) subtracting the predicted tube wave data set qm(t,k) from the original seismic data set pm(t,k) to obtain a set of corrected seismic data pcm(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;
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- (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.
Dependencies are inferred from the claim text.