The anisotropic properties of subsurface media cause waveform distortions in seismic wave propagation,resulting in a negative infl uence on seismic imaging.In addition,wavefields simulated by the conventional coupled ...The anisotropic properties of subsurface media cause waveform distortions in seismic wave propagation,resulting in a negative infl uence on seismic imaging.In addition,wavefields simulated by the conventional coupled pseudo-acoustic equation are not only aff ected by SV-wave artifacts but are also limited by anisotropic parameters.We propose a least-squares reverse time migration(LSRTM)method based on the pure q P-wave equation in vertically transverse isotropic media.A fi nite diff erence and fast Fourier transform method,which can improve the effi ciency of the numerical simulation compared to a pseudo-spectral method,is used to solve the pure q P-wave equation.We derive the corresponding demigration operator,migration operator,and gradient updating formula to implement the LSRTM.Numerical tests on the Hess model and field data confirm that the proposed method has a good correction eff ect for the travel time deviation caused by underground anisotropic media.Further,it signifi cantly suppresses the migration noise,balances the imaging amplitude,and improves the imaging resolution.展开更多
最小二乘逆时偏移(Least-Square Reverse Time Migration,LSRTM)相比于常规偏移具有更高的成像分辨率、振幅保幅性及均衡性等优势,是当前研究的热点之一.然而,目前LSRTM算法大多是基于二阶常密度标量声波方程建立的,忽略了密度变化对振...最小二乘逆时偏移(Least-Square Reverse Time Migration,LSRTM)相比于常规偏移具有更高的成像分辨率、振幅保幅性及均衡性等优势,是当前研究的热点之一.然而,目前LSRTM算法大多是基于二阶常密度标量声波方程建立的,忽略了密度变化对振幅的影响,因而基于振幅匹配策略的常规LSRTM很难在变密度介质下取得保真的成像结果.一阶速度-应力方程能够很好地处理变密度介质,但简单地将一阶速度-应力方程应用到LSRTM中缺乏理论基础.为此,本文从LSRTM的正问题入手,提出了基于交错网格的一阶速度-应力方程LSRTM理论方法.首先将一阶波动方程线性化,建立了一阶方程LSRTM的目标泛函,随后推导其伴随方程,并借助伴随状态法给出了迭代更新流程,最终建立了基于一阶速度-应力方程LSRTM的理论框架.进一步,通过在相位编码LSRTM中引入随机最优化思想,极大地减小了计算量、提高了计算效率.最后,通过模型试算验证了本算法的正确性和有效性.展开更多
在复杂构造、复杂岩性、复杂地表条件等地区进行油气地震勘探面临诸多难题,其中剧烈起伏的地表已成为制约上述地区地震勘探发展的瓶颈之一。最小二乘逆时偏移(Least-Squares Reverse Time Migration,LSRTM)相对于常规偏移具有更高的成...在复杂构造、复杂岩性、复杂地表条件等地区进行油气地震勘探面临诸多难题,其中剧烈起伏的地表已成为制约上述地区地震勘探发展的瓶颈之一。最小二乘逆时偏移(Least-Squares Reverse Time Migration,LSRTM)相对于常规偏移具有更高的成像分辨率、振幅保真性及均衡性等优势,但基于矩形网格的LSRTM在面对复杂地表时无法很好地适用山前带等剧烈起伏地形。此外,山前带地震资料中包含较多的噪声,T分布相比Huber范数和混合模,在缺失数据的条件下更稳健,且没有多余参数,因而简单实用,而Huber范数和混合模的结果严重依赖参数选取,需要大量的尝试。为此,将全交错网格引入贴体网格,将T分布推广到起伏地表LSRTM,进一步推导了贴体网格线性Born正演方程,在此基础上提出了基于贴体全交错网格的起伏地表LSRTM算法,较好地克服了起伏地形的影响。模型试算验证了算法的有效性和对复杂模型的适应性。展开更多
基金financially supported by the National Key R&D Program of China (No. 2019YFC0605503)the Major Scientific and Technological Projects of CNPC (No. ZD2019-183-003)the National Natural Science Foundation of China (No. 41922028,41874149)。
文摘The anisotropic properties of subsurface media cause waveform distortions in seismic wave propagation,resulting in a negative infl uence on seismic imaging.In addition,wavefields simulated by the conventional coupled pseudo-acoustic equation are not only aff ected by SV-wave artifacts but are also limited by anisotropic parameters.We propose a least-squares reverse time migration(LSRTM)method based on the pure q P-wave equation in vertically transverse isotropic media.A fi nite diff erence and fast Fourier transform method,which can improve the effi ciency of the numerical simulation compared to a pseudo-spectral method,is used to solve the pure q P-wave equation.We derive the corresponding demigration operator,migration operator,and gradient updating formula to implement the LSRTM.Numerical tests on the Hess model and field data confirm that the proposed method has a good correction eff ect for the travel time deviation caused by underground anisotropic media.Further,it signifi cantly suppresses the migration noise,balances the imaging amplitude,and improves the imaging resolution.
文摘最小二乘逆时偏移(Least-Square Reverse Time Migration,LSRTM)相比于常规偏移具有更高的成像分辨率、振幅保幅性及均衡性等优势,是当前研究的热点之一.然而,目前LSRTM算法大多是基于二阶常密度标量声波方程建立的,忽略了密度变化对振幅的影响,因而基于振幅匹配策略的常规LSRTM很难在变密度介质下取得保真的成像结果.一阶速度-应力方程能够很好地处理变密度介质,但简单地将一阶速度-应力方程应用到LSRTM中缺乏理论基础.为此,本文从LSRTM的正问题入手,提出了基于交错网格的一阶速度-应力方程LSRTM理论方法.首先将一阶波动方程线性化,建立了一阶方程LSRTM的目标泛函,随后推导其伴随方程,并借助伴随状态法给出了迭代更新流程,最终建立了基于一阶速度-应力方程LSRTM的理论框架.进一步,通过在相位编码LSRTM中引入随机最优化思想,极大地减小了计算量、提高了计算效率.最后,通过模型试算验证了本算法的正确性和有效性.
文摘在复杂构造、复杂岩性、复杂地表条件等地区进行油气地震勘探面临诸多难题,其中剧烈起伏的地表已成为制约上述地区地震勘探发展的瓶颈之一。最小二乘逆时偏移(Least-Squares Reverse Time Migration,LSRTM)相对于常规偏移具有更高的成像分辨率、振幅保真性及均衡性等优势,但基于矩形网格的LSRTM在面对复杂地表时无法很好地适用山前带等剧烈起伏地形。此外,山前带地震资料中包含较多的噪声,T分布相比Huber范数和混合模,在缺失数据的条件下更稳健,且没有多余参数,因而简单实用,而Huber范数和混合模的结果严重依赖参数选取,需要大量的尝试。为此,将全交错网格引入贴体网格,将T分布推广到起伏地表LSRTM,进一步推导了贴体网格线性Born正演方程,在此基础上提出了基于贴体全交错网格的起伏地表LSRTM算法,较好地克服了起伏地形的影响。模型试算验证了算法的有效性和对复杂模型的适应性。
