【摘要】 依赖于偏移距的反射波调谐是AVO分析的不利因素.无论动校正还是偏移,都会引起子波拉伸、频谱向低频移动.在频率域对动校正或偏移后的地震数据进行反拉伸校正是本文消除子波拉伸采用的方法.从射线参数时距方程出发推导的地震映射压缩因子与反射角存在较精确的余弦关系.角度道中动校正或偏移子波拉伸因子是反射角余弦的倒数.用无拉伸子波频谱除以拉伸子波频谱得到反频谱压缩算子,对动校正或偏移后存在子波拉伸的角度道应用反频谱压缩算子,操作简单易行.薄层模型试验和实际地震资料处理表明角度道校正方法能够消除子波拉伸畸变,展宽频谱,补偿地震资料动校正或偏移过程中丢失的高频成分,提高大角度的分辨率和保真度,改善AVO分析.更多还原

【Abstract】 Offset-dependent tuning includes seismic imaging tuning,NMO stretch,and migration stretch.Seismic imaging tuning caused by compression of reflectivity inheres in seismic record.Either NMO stretch or migration stretch is the wavelet stretch which arises in the seismic processing.They are adverse factors for AVO analysis.The goal of dynamic correction or migration is to modify the time difference measured at the mid- and the far-offset trace to that at the near-offset trace.Either dynamic correction or migration stretches the compressed reflectivity,but brings wavelet stretch and corresponding spectral compression at the same time.The method of removing wavelet stretch proposed in this article is to do anti-stretch correction on the seismic data after dynamic correction or migration in frequency domain.The compression factor of seismic imaging tuning deduced from the parametric ray equations is related closely to the cosine of the refection angle.In offset traces after dynamic correction or migration,the wavelet stretch factor which varies with time and velocity is nonstationary.The shallow reflection at the far offset has a large stretch.However,in angle traces after dynamic correction or migration the wavelet stretch factor is the reciprocal of the cosine of the refection angle.It s feasible to correct wavelet stretch in angle traces by applying stationary inverse spectral operators which can be obtained by stretch-free wavelet spectrum divided by stretched wavelet spectrum. Thin-bed model test and real date processing show that the method of wavelet stretch correction in angle traces can eliminate the distortion of the wavelet,increase the spectral bandwidth,compensate the high frequency components lost in dynamic correction or migration,increase the resolution and the fidelity of large angles and improve AVO analysis.NMO or migration stretch mute on shallow reflection data is not as necessary as before.The wavelet stretch correction can bring great benefits to wide-angle seismic exploration.更多还原