Method for separating harmonic waves of sleeves

Abstract

The invention discloses a method for separating harmonic waves in sleeves in seismic exploration. Median filtering and band-pass filtering are combined by the aid of differences among apparent velocities of seismic waves in the method. The method includes picking up an initial time point and a first time point from original data, adding the initial time point and the first time point of a trace of the original data to time points of various sampling points and leveling upward traveling waves to obtain a first wave field; performing filtering for the first wave field by the aid of an initial time point, a first time point and a second time point of the first wave field to obtain a second wave field; performing Fourier transformation to filter out signals outside frequency bands to obtain a third wave field; subtracting the third wave field from the first wave field to obtain a fourth wave field, picking up a horizontal even in the fourth wave field and performing filtering along a depth direction to obtain a fifth wave field; filtering signals outside frequency bands to obtain a sixth wave field; subtracting the sixth wave field from the fourth wave field to obtain a seventh wave field; repeating the process from a third step to a seventh step once by using the seventh wave field as a first wave field to obtain an eighth wave field; performing filtering by the aid of an initial time point and a first time point to obtain a ninth wave field; subtracting the initial time point and the first time point of the sampling points in each trace from the time points of the sample points to obtain a tenth wave field; and subtracting the tenth wave field from the original data to separate the harmonic waves. The method has the advantages that only seismic waves containing harmonic interference are suppressed, the harmonic waves of the sleeves are effectively separated, and seismic traces without harmonic interference cannot be damaged.

Description

technical field [0001] The invention relates to a seismic exploration data processing technology, which is a casing harmonic separation method using the apparent velocity difference of seismic waves combined with median filtering and band-pass filtering. Background technique [0002] Due to the special acquisition method and poor cementing quality of vertical seismic profiling (VSP) data, strong casing harmonic interference is often generated in the records, which will greatly reduce the signal-to-noise ratio of the data. [0003] In current VSP data processing, there is no targeted method to suppress casing harmonics before wave field separation. In the wave field separation, the downgoing waves are aligned mainly according to the first arrival time of each trace, and the median filtering is performed in the depth direction to obtain the downgoing waves, and then the reverse time shift is performed to obtain the final downgoing wave profile. The residual wave field is obta...

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Problems solved by technology

Since the energy of the harmonic is very strong, and the median filter is a kind of statistical filter, it has a certain smoothing effect. In the process of two median filters, the energy relationship of the adjacent channel where the harmonic is located will be changed each time, thus changing Wave resistance characteristics, it is difficult to obtain a good processing effect, which affects the later processing and interpretation

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