Prestack reverse time migration（PSTM） is a common imaging method; however low-frequency noises reduce the structural imaging precision. Thus, the suppression of migration noises must be considered. The generation me...Prestack reverse time migration（PSTM） is a common imaging method; however low-frequency noises reduce the structural imaging precision. Thus, the suppression of migration noises must be considered. The generation mechanism of low-frequency noises is analyzed and the up-, down-, left-, and right-going waves are separated using the Poynting vector of the acoustic wave equation. The computational complexity and memory capacitance of the proposed method are far smaller than that required when using the conventional separation algorithm of 2D Fourier transform. The normalized wavefield separation crosscorrelation imaging condition is used to suppress low-frequency noises in reverse time migration and improve the imaging precision. Numerical experiments using the Marmousi model are performed and the results show that the up-, down-, left-, and right-going waves are well separated in the continuation of the wavefield using the Poynting vector. We compared the imaging results with the conventional method, Laplacian filtering, and wavefield separation with the 2D Fourier transform. The comparison shows that the migration noises are well suppressed using the normalized wavefield separation cross-correlation imaging condition and higher precision imaging results are obtained.展开更多
Based on arbitrarily wide-angle wave equations,a reverse-time propagation scheme is developed by substituting the partial derivatives of depth and time with central differences. The partial derivative of horizontal di...Based on arbitrarily wide-angle wave equations,a reverse-time propagation scheme is developed by substituting the partial derivatives of depth and time with central differences. The partial derivative of horizontal direction is replaced with high order difference. The imaging condition is computed by solving the eikonal equations. On the basis of above techniques,a prestack reverse-time depth migration algorithm is developed. The processing exam-ples of synthetic data show that the method can remove unwanted internal reflections and decrease the migration noise. The method also has the advantage of fidelity and is applicable of dip angle reflector imaging.展开更多
波动方程有限差分数值模拟是研究地震波在地下介质中的波场特征和传播机理的重要手段。对于常规有限差分技术,当采用大网格对计算空间进行差分离散时会出现严重的数值频散问题,降低了计算精度。通量校正(Flux-corrected transport metho...波动方程有限差分数值模拟是研究地震波在地下介质中的波场特征和传播机理的重要手段。对于常规有限差分技术,当采用大网格对计算空间进行差分离散时会出现严重的数值频散问题,降低了计算精度。通量校正(Flux-corrected transport method,FCT)技术能够有效压制粗网格情况下有限差分的数值频散。本文研究了具有垂直对称轴横向各向同性(Vertical Transverse Isotropy,VTI)介质的交错网格FCT有限差分技术。首先从一阶速度—应力弹性波方程出发,在交错网格空间中给出了该方程的高阶有限差分法格式及稳定性条件,在此基础上研究了波动方程正演过程中的数值频散FCT压制技术,二者结合实现了该方程的高精度有限差分数值模拟。同常规算法相比,本文算法不额外增加内存需求,少量增加计算量,但可有效压制VTI介质中弹性波动方程正演的数值频散现象。当采用大网格进行数值模拟时,本文方法明显提高了波场模拟精度。展开更多
基金supported by the National Natural Science Foundation of China(No.41174087,41204089)the National Oil and Gas Major Project(No.2011ZX05005-005)
文摘Prestack reverse time migration（PSTM） is a common imaging method; however low-frequency noises reduce the structural imaging precision. Thus, the suppression of migration noises must be considered. The generation mechanism of low-frequency noises is analyzed and the up-, down-, left-, and right-going waves are separated using the Poynting vector of the acoustic wave equation. The computational complexity and memory capacitance of the proposed method are far smaller than that required when using the conventional separation algorithm of 2D Fourier transform. The normalized wavefield separation crosscorrelation imaging condition is used to suppress low-frequency noises in reverse time migration and improve the imaging precision. Numerical experiments using the Marmousi model are performed and the results show that the up-, down-, left-, and right-going waves are well separated in the continuation of the wavefield using the Poynting vector. We compared the imaging results with the conventional method, Laplacian filtering, and wavefield separation with the 2D Fourier transform. The comparison shows that the migration noises are well suppressed using the normalized wavefield separation cross-correlation imaging condition and higher precision imaging results are obtained.
文摘Based on arbitrarily wide-angle wave equations,a reverse-time propagation scheme is developed by substituting the partial derivatives of depth and time with central differences. The partial derivative of horizontal direction is replaced with high order difference. The imaging condition is computed by solving the eikonal equations. On the basis of above techniques,a prestack reverse-time depth migration algorithm is developed. The processing exam-ples of synthetic data show that the method can remove unwanted internal reflections and decrease the migration noise. The method also has the advantage of fidelity and is applicable of dip angle reflector imaging.
文摘波动方程有限差分数值模拟是研究地震波在地下介质中的波场特征和传播机理的重要手段。对于常规有限差分技术,当采用大网格对计算空间进行差分离散时会出现严重的数值频散问题,降低了计算精度。通量校正(Flux-corrected transport method,FCT)技术能够有效压制粗网格情况下有限差分的数值频散。本文研究了具有垂直对称轴横向各向同性(Vertical Transverse Isotropy,VTI)介质的交错网格FCT有限差分技术。首先从一阶速度—应力弹性波方程出发,在交错网格空间中给出了该方程的高阶有限差分法格式及稳定性条件,在此基础上研究了波动方程正演过程中的数值频散FCT压制技术,二者结合实现了该方程的高精度有限差分数值模拟。同常规算法相比,本文算法不额外增加内存需求,少量增加计算量,但可有效压制VTI介质中弹性波动方程正演的数值频散现象。当采用大网格进行数值模拟时,本文方法明显提高了波场模拟精度。
