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在分析地震反射波勘探信号小波包分解特性的基础上,提出了基于小波包分解的地层吸收补偿方法.如果没有地层吸收,浅层反射波和深层反射波具有相同的振幅谱而相位谱相差一线性相位.如果把地震记录分成不同的频段,不同频段对于时间的能量分布关系具有相似性,即对所有频段的深层反射的能量与同一频段浅层反射能量之比应该相同;只是不同频段的绝对能量大小不一样.由于地层的吸收造成各频段能量对时间的分布不同,如果给这些频段乘以时变权使各频段能量对时间的分布相同,就起到了对地层吸收的补偿作用.该方法首先用小波包对地震勘探信号进行分频,然后根据地层吸收的特点,在每一个频段上分别提取每一个时间点的吸收系数并用其倒数加权每一个小波包系数,再用加权后的小波包系数重构地震反射波记录消除地层吸收.该方法适合Q值未知的情况,对变Q和常Q都能适应.从实际应用效果看,该方法能很好的补偿地层的吸收。
On the basis of analyzing wavelet packet decomposition characteristics of seismic reflection signal, a new method of compensation based on wavelet packet decomposition is proposed. If there is no formation absorption, the shallow reflection and the deep reflection have the same amplitude spectrum and the phase spectrum differs by a linear phase. If the seismic records are divided into different frequency bands, the energy distributions of different frequency bands with respect to time have similarities, that is, the ratio of the energy of deep reflection in all frequency bands to the energy of shallow reflection in the same frequency band should be the same; only the absolute energy of different frequency bands same. Due to the absorption of the strata, the distribution of the energies over time in different frequency bands is different. If these frequency bands are multiplied by time-varying weights, the distribution of the energy in each frequency band to time is the same, which compensates for the strata absorption. In this method, the seismic exploration signal is first divided by wavelet packet. Then, the absorption coefficients of each time point are extracted in each frequency band according to the characteristics of formation absorption, and each wavelet packet coefficient is weighted by the reciprocal of each. Then the weighted Wavelet Packet Coefficients Reconstruct Seismic Reflected Wave Records to Eliminate Formation Absorption. The method is suitable for the case of unknown Q value, which can be adapted to Q and Q. From the practical application effect, this method can well compensate the strata absorption.