基于两步扫描法的Kirchhoff时间最优偏移孔径

Optimal migration aperture of Kirchhoff time based on two-step scanning method

倾角域稳相菲涅尔带的确定依赖于预先设定的判别阈值,需要反复优选设定。在偏移过程中引入拉伸畸变校正因子和加权补偿因子,完成浅层拉伸畸变校正和深、浅层振幅均衡处理,得到高质量倾角道集;根据导出的2D菲涅尔带计算公式,以最佳叠加能量为判别准则,采用两步扫描法研究菲涅尔带影响因素——成像倾角和地震波主频,自适应地确定成像点处成像倾角及菲涅尔带范围,建立基于数据驱动的最优偏移孔径确定方法。常孔径和扫描孔径偏移结果局部对比和信噪比分析结果表明:基于两步扫描法的最优偏移孔径成像剖面中偏移噪声得到较好压制,信噪比提高7.37dB,地质构造成像更加清晰。基于两步扫描法的最优偏移孔径确定方法正确、有效,可提升叠前时间偏移成像质量。

Determination of the Fresnel zone of stationary phase points in the dip angle domain relies on preset discriminative thresholds,and it is necessary to use trial and error to optimize the discriminative thresholds in advance,which brings inconvenience to actual data processing.To solve that problem,firstly,we automatically removed the stretching distortion in data of shallow and compensated the amplitude difference between data of deep and shallow by introducing the stretching distortion factor,and amplituded weighting factor in the process of migration.We established the high-quality dip angle gathers.On that basis,we determined the optimal imaging dip angle and associated Fresnel zone adaptively by performing two-step scanning of the controlling factors(imaging dip angle and the dominant frequency of seismic wave) of Fresnel zone according to the formula of 2D Fresnel zone,based on the criterion of optimum stacked energy.The established method of determining the optimum migration aperture is all based on data-driven.The local contrast and SNR quantitative analysis results of the migration profiles with constant aperture and scanned optimum aperture show that: the migration noise is well suppressed in migration profile with optimum aperture scanned by two steps,the SNR is improved by 7.37 dB,and the imaging of geological structure is clearer.The method of determining the optimum migration aperture based on two-step scanning method is correct and effective,and it can well improve the imaging quality of prestack time migration.