构造导向的深度偏移井震误差校正方法

    Structure-oriented log-seismic error correction in prestack depth migration

    • 摘要: 井震误差校正是求取VTI介质的Thomsen纵波各向异性参数的主要方法,也是获得准确的深度偏移成像的重要处理手段。常规的井震误差校正方法是求取井点处的井震误差,然后直接沿平面插值对层位深度进行校正,但这种校正方法在地层厚度变化较大的地方容易出现构造畸变和各向异性参数δ的异常值。常用的解决方法是对各向异性参数场和各向异性速度场进行人工编辑和平滑,但这样会浪费较多的人力和时间。本文提出了构造导向的井震误差校正方法,引入“井震误差系数”的概念,用地层厚度进行约束来对井震误差进行平面插值,并且对不同地层的井震误差采用从浅到深依次计算并插值的策略。这种方法得到的井震误差分布值更符合地层厚度的变化规律,求取的各向异性参数δ值更加稳定且无异常值,有效地避免了井震误差校正后出现构造畸变,在实际项目运作中节省了人力和时间。

       

      Abstract: Log-seismic error correction serves as a primary method for determining Thomsen's compressional-wave anisotropic parameters of vertical transverse isotropy(VTI) media.This method is also an essential processing technique for obtaining accurate depth-migrated images.Conventional log-seismic error correction involves determining the log-seismic errors at well locations and then directly applying planar interpolation to correct the depths of seismic horizons.However,the conventional method can lead to structural distortions and anomalous values of anisotropic parameter δ in areas with significantly varying formation thicknesses.To address this issue,researchers typically manually edit and smooth the anisotropic parameter field and the anisotropic velocity field,consuming considerable manpower and time.Hence,this study proposed a structure-oriented log-seismic error correction method that incorporates the concept of log-seismic error coefficient.The proposed method utilizes formation thicknesses as constraints to perform planar interpolation for log-seismic errors.Moreover,it employs a strategy of sequential calculation and interpolation for log-seismic errors from shallow to deep formations.It yielded log-seismic error distribution values that better conform to formation thickness variations and more stable δ values,without anomalous values.Therefore,the proposed method effectively avoids structural distortions induced by log-seismic error correction while saving manpower and time in practical projects.

       

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