基于弱反射方程和特征值分解的叠前逆时偏移噪声压制
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摘要
采用双程波动方程的逆时偏移可以使成像不受构造倾角限制且精度较高,但双程波动方程的采用使地震波在分界面处产生反射,在偏移过程中产生低频干扰,尤其在浅层更为严重,从而使得成像剖面中出现噪声。通过研究弱反射方程和特征值分解法,采用基于特征值分解的一阶压力速度弱反射方程压制叠前逆时偏移噪声。通过理论模型分析表明:该方法不但保持了偏移成像不受构造倾角限制且精度较高的优点,而且有效地压制了界面反射波,从而消除逆时偏移过程中产生的低频干扰,使成像效果有显著的改善。
Pre-stack reverse-time migration using two-way wave equation can bring high image accuracy and is not restricted by structural obliquity.But owing to using two-way wave equation,seismic waves in the medium have the reflection at the interface,engendering low-frequency disturbance during migration,especially in shallow lays,and producing some noise in migration section.We propose the method,that is,the first-order weak reflection equation of pressure-speed is combined with eigenvalue decomposition,through the research of both the weak reflection equation and eigenvalue decomposition methods.The theoretical model analyses show that,this approach can not only get high accuracy imaging without being restricted by structural obliquity,but also effectively suppress the interface reflected wave in the process of reverse-time migration,consequently eliminating low-frequency disturbance generated by the interface reflected wave in the imaging.So it has a very marked improvement to the effect of imaging.
Pre-stack reverse-time migration using two-way wave equation can bring high image accuracy and is not restricted by structural obliquity.But owing to using two-way wave equation,seismic waves in the medium have the reflection at the interface,engendering low-frequency disturbance during migration,especially in shallow lays,and producing some noise in migration section.We propose the method,that is,the first-order weak reflection equation of pressure-speed is combined with eigenvalue decomposition,through the research of both the weak reflection equation and eigenvalue decomposition methods.The theoretical model analyses show that,this approach can not only get high accuracy imaging without being restricted by structural obliquity,but also effectively suppress the interface reflected wave in the process of reverse-time migration,consequently eliminating low-frequency disturbance generated by the interface reflected wave in the imaging.So it has a very marked improvement to the effect of imaging.
引文
[1]Whitmore N D.Iterative depth migration by backward time propagation[C]//53th SEG Annual Meeting.Las Vegas,1983:382-385.
[2]Baysal E,Kosloff D D.Sherwood J W C.Reverse time migration[J].Geophysics,1983,48(11):1514-1524.
[3]Loewenthal D,Mufti I R.Reverse time migration in spatial frequency domain[J].Geophysics,1983,48(5):627-635.
[4]Chang W F,McMechan G A.Reverse migration of offset vertical seismic profiling data using the excitation time imaging condition[J].Geophysics,1986,51(1):67-84.
[5]Sun R,McMechan G A.Pre-stack reverse-time migration for elastic with application to synthetic offset vertical seismic profiles[J].Proceedings of the IEEE,1986,74(3):457-465.
[6]DONG Zhengxin,McMechan A.3-D prestack migration in anisotropic media[J].Geophysics,1993,58(1):79-90.
[7]Baysal E,Kosloff D D,Sherwood J.A two-way nonreflecting wave equation[J].Geophysics,1984,49(2):132-141.
[8]王山山,聂勋碧,邓玉琼.混合法双程无反射波动方程偏移[J].石油地球物理勘探,1993,28(5):537-544.WANG Shanshan,NIE Xunbi,DENG Yuqiong.Hybrid migration using two-way nonrefleeting wave equation[J].Oil Geophysical Prospecting,1993,28(5):537-544.
[9]吴清岭,李伟,陈可为,等.无反射波动方程正演模型及其应用[J].石油地球物理勘探,2000,35(2):147-154.WU Qingling,LI Wei,CHEN Kewei,et al.Reflection-free wave equation modeling and its application[J].Oil Geophysical Prospecting,2000,35(2):147-253.
[10]Guitton A,Kaelin B,Biondi B.Least-squares attenuation of reverse-time-migration artifacts[J].Geophysics,2007,72(1):S19-S23.
[11]Mulder W A,Plessix R E.A comparison between one-way and two-way wave-equation migration[J].Geophysics,2006,69(6):1491-1504.
[12]Fletcher R F,Fowler P,Kitchenside P,et al.Suppressing artifacts in prestack reverse time migration[C]//75th SEG Annual Meeting.2005:2049-2052.
[13]XIE Xiaobi,WU Rushan.A depth migration method based on the full-wave reverse-time calculation and local one-way propagation[C]//76th SEG Annual Meeting.New Orleans,2006:2333-2337.
[14]Yoon K,Marfurt K J.Revesrse-time migration using the pointing vector[J].Exploration Geophysics,2006,59(1):102-107.
[15]杜启振,秦童.横向各向同性介质弹性波多分量叠前逆时偏移[J].地球物理学报,2009,52(3):501-807.DU Qizheng,QIN Tong.Multicomponent prestack reverse-time migration of elastic waves in transverse isotropic medium[J].Chines J Geophys,2009,52(3):501-807.
[16]董良国.弹性波数值模拟中的吸收边界条件[J].石油地球物理勘探,1999,34(1):45-56.DONG Liangguo.Absorptive boundary condition in elastic-wave numerical modeling[J].Oil Geophysical Prospecting,1999,34(1):45-56.
[2]Baysal E,Kosloff D D.Sherwood J W C.Reverse time migration[J].Geophysics,1983,48(11):1514-1524.
[3]Loewenthal D,Mufti I R.Reverse time migration in spatial frequency domain[J].Geophysics,1983,48(5):627-635.
[4]Chang W F,McMechan G A.Reverse migration of offset vertical seismic profiling data using the excitation time imaging condition[J].Geophysics,1986,51(1):67-84.
[5]Sun R,McMechan G A.Pre-stack reverse-time migration for elastic with application to synthetic offset vertical seismic profiles[J].Proceedings of the IEEE,1986,74(3):457-465.
[6]DONG Zhengxin,McMechan A.3-D prestack migration in anisotropic media[J].Geophysics,1993,58(1):79-90.
[7]Baysal E,Kosloff D D,Sherwood J.A two-way nonreflecting wave equation[J].Geophysics,1984,49(2):132-141.
[8]王山山,聂勋碧,邓玉琼.混合法双程无反射波动方程偏移[J].石油地球物理勘探,1993,28(5):537-544.WANG Shanshan,NIE Xunbi,DENG Yuqiong.Hybrid migration using two-way nonrefleeting wave equation[J].Oil Geophysical Prospecting,1993,28(5):537-544.
[9]吴清岭,李伟,陈可为,等.无反射波动方程正演模型及其应用[J].石油地球物理勘探,2000,35(2):147-154.WU Qingling,LI Wei,CHEN Kewei,et al.Reflection-free wave equation modeling and its application[J].Oil Geophysical Prospecting,2000,35(2):147-253.
[10]Guitton A,Kaelin B,Biondi B.Least-squares attenuation of reverse-time-migration artifacts[J].Geophysics,2007,72(1):S19-S23.
[11]Mulder W A,Plessix R E.A comparison between one-way and two-way wave-equation migration[J].Geophysics,2006,69(6):1491-1504.
[12]Fletcher R F,Fowler P,Kitchenside P,et al.Suppressing artifacts in prestack reverse time migration[C]//75th SEG Annual Meeting.2005:2049-2052.
[13]XIE Xiaobi,WU Rushan.A depth migration method based on the full-wave reverse-time calculation and local one-way propagation[C]//76th SEG Annual Meeting.New Orleans,2006:2333-2337.
[14]Yoon K,Marfurt K J.Revesrse-time migration using the pointing vector[J].Exploration Geophysics,2006,59(1):102-107.
[15]杜启振,秦童.横向各向同性介质弹性波多分量叠前逆时偏移[J].地球物理学报,2009,52(3):501-807.DU Qizheng,QIN Tong.Multicomponent prestack reverse-time migration of elastic waves in transverse isotropic medium[J].Chines J Geophys,2009,52(3):501-807.
[16]董良国.弹性波数值模拟中的吸收边界条件[J].石油地球物理勘探,1999,34(1):45-56.DONG Liangguo.Absorptive boundary condition in elastic-wave numerical modeling[J].Oil Geophysical Prospecting,1999,34(1):45-56.
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