VTI介质角度叠加逆时偏移
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摘要
常规各向同性逆时偏移方法在处理各向异性问题时会导致层位成像不准确、同相轴能量不聚焦等问题,并且利用拉普拉斯滤波算子等简单滤波方法不能彻底去除成像结果中的强振幅低频噪声。针对这些问题,首先应用声波近似方程模拟qP波在各向异性VTI介质中的传播,在震源激发位置设定平滑的各向同性或椭圆各向异性震源环以压制qSV波的影响;在此基础上提出了VTI介质逆时偏移的角度叠加实现策略,利用角度域共成像点道集中不同角度成像结果的叠加压制低频噪声,提高成像精度。模型试算和应用实例偏移结果表明,该方法能够对高陡复杂构造准确成像,且能量均衡、低频噪声压制效果较好。
Conventional isotropic reverse time migration(RTM)method can lead to inaccurate imaging and unfocused seismic event energy when dealing with the anisotropic problem,and the strong amplitude and low frequency noise in the RTM imaging results cannot be completely removed by simple filtering methods such as Laplace filter operator.In order to solve these problems,we apply acoustic approximate equation to simulate the wavefield propagation of qP wave in VTI medium,eliminate the influence of qSV wave through setting smooth isotropic or elliptic anisotropic source ring at source locations.On this basis,the angle domain common imaging gathers(ADCIGs)superposition implementation strategies of RTM in VTI medium has been developed,which use the superposition of imaging results with different angles in ADCIGs to suppress the low-frequency noise and improve the imaging precision.Model tests and real dataset examples verify that the proposed approach can obtain the accurate imaging in complex steep structures with better energy balance and lower low-frequency noise.
Conventional isotropic reverse time migration(RTM)method can lead to inaccurate imaging and unfocused seismic event energy when dealing with the anisotropic problem,and the strong amplitude and low frequency noise in the RTM imaging results cannot be completely removed by simple filtering methods such as Laplace filter operator.In order to solve these problems,we apply acoustic approximate equation to simulate the wavefield propagation of qP wave in VTI medium,eliminate the influence of qSV wave through setting smooth isotropic or elliptic anisotropic source ring at source locations.On this basis,the angle domain common imaging gathers(ADCIGs)superposition implementation strategies of RTM in VTI medium has been developed,which use the superposition of imaging results with different angles in ADCIGs to suppress the low-frequency noise and improve the imaging precision.Model tests and real dataset examples verify that the proposed approach can obtain the accurate imaging in complex steep structures with better energy balance and lower low-frequency noise.
引文
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[13] 唐永杰,宋桂桥,刘少勇,等.基于波长平滑算子的逆时偏移回转波假象去除方法[J].石油地球物理勘探,2018,53(1):80-86.TANG Yongjie,SONG Guiqiao,LIU Shaoyong,et al.Turning wave false image removal based on wavelength-dependent smoothing operator in reverse time migration[J].Oil Geophysical Prospecting,2018,53(1):80-86.
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[19] 杨富森,李振春,王小丹,等.等价各向异性介质一阶拟声波方程正演模拟及其效率分析[J].地震学报,2015,37(4):648-660.YANG Fusen,LI Zhenchun,WANG Xiaodan,et al.Equivalent anisotropic first-order pseudo-acoustic wave equations modeling and its efficiency analysis[J].Acta Seismologica Sinica,2015,37(4):648-660.
[20] Yoon K,Marfurt K J.Reverse-time migration using the Poynting vector[J].Exploration Geophysics,2006,59(1):102-107.
[21] Costa J C,Silva Neto F A,Alcabtara M R,et al.Obliquity-correction imaging condition for reverse time migration[J].Geophysics,2009,74(3):S57-S66.
[22] 李海强,杨国权,李振春,等.基于局部平面波分解的逆时偏移角道集提取方法[J].石油地球物理勘探,2017,52(6):1177-1183.LI Haiqiang,YANG Guoquan,LI Zhenchun,et al.A method for extracting angle-domain common-image gathers based on local plane wave decomposition[J].Oil Geophysical Prospecting,2017,52(6):1177-1183.
[23] Thomsen L.Weak elastic anisotropics[J].Geophy-sics,1986,51(10):1954-1966.
[24] Du X,Fletcher R,Fowler P J.A new pseudo-acoustic wave equation for VTI media[C].Extended Abstracts of 70th EAGE Conference & Exhibition,2008,1024-1028.
[25] Hestholm S.Acoustic VTI modeling using high-order finite differences[J].Geophysics,2009,74(5):T67-T73.
[2] 张慧,蔡其新,秦广胜,等.基于GPU并行加速的逆时偏移成像方法[J].石油地球物理勘探,2013,48(5):707-710.ZHANG Hui,CAI Qixin,QIN Guangsheng,et al.GPU-accelerated reverse time migration and its application[J].Oil Geophysical Prospecting,2013,48(5):707-710.
[3] 刘文卿,王宇超,雍学善,等.基于GPU/CPU叠前逆时偏移研究及应用[J].石油地球物理勘探,2012,47(5):712-716.LIU Wenqing,WANG Yuchao,YONG Xueshan,et al.Prestack reverse time migration on GPU/CPU co-parallel computation[J].Oil Geophysical Prospecting,2012,47(5):712-716.
[4] 唐祥功,匡斌,杜继修,等.多GPU协同三维叠前逆时偏移方法研究与应用[J].石油地球物理勘探,2013,48(6):910-914.TANG Xianggong,KUANG Bin,DU Jixiu,et al.3D prestack reverse time migration based on multiple-GPU collaboration[J].Oil Geophysical Prospecting,2013,48(6):910-914.
[5] 杨午阳,张厚柱,撒利明,等.逆时偏移关键问题探讨[J].石油地球物理勘探,2016,51(6):1251-1262.YANG Wuyang,ZHANG Houzhu,SA Liming,et al.Some issues about reverse time migration[J].Oil Geo-physical Prospecting,2016,51(6):1251-1262.
[6] 魏石磊,张大洲,李明智,等.VTI介质中波场分离算子特征研究[J].石油地球物理勘探,2016,51(3):506-512.WEI Shilei,ZHANG Dazhou,LI Mingzhi,et al.Wave field separation operator characteristics in the VTI media[J].Oil Geophysical Prospecting,2016,51(3):506-512.
[7] 杨富森,李振春,王小丹.TTI介质一阶qP波稳定方程波场数值模拟及逆时偏移[J].石油地球物理勘探,2016,51(3):497-505.YANG Fusen,LI Zhenchun,WANG Xiaodan.Wave-field numerical simulation and reverse-time migration based on the stable TTI first-order qP-wave equations[J].Oil Geophysical Prospecting,2016,51(3):497-505.
[8] 王鹏飞,何兵寿.基于行波分离的三维弹性波矢量场点积互相关成像条件[J].石油地球物理勘探,2017,52(3):477-483.WANG Pengfei,HE Bingshou.Vector field dot pro-duct cross-correlation imaging based on 3D elastic wave separation[J].Oil Geophysical Prospecting,2017,52(3):477-483.
[9] Robert G C.Reverse time migration with random boundary[C].SEG Technical Program Expanded Abstracts,2009,28:2809-2813.
[10] Zhang Y,Sun J.Practical issues in reverse time migration:true amplitude gathers,noise removal and harmonic source encoding[J].First Break,2009,26(1):29-35.
[11] 刘红伟,刘洪,邹振.地震叠前逆时偏移中的去噪与存储[J].地球物理学报,2010,53(9):2171-2180.LIU Hongwei,LIU Hong,ZOU Zhen.The problems of denoise and storage in seismic reverse time migration[J].Chinese Journal of Geophysics,2010,53(9):2171-2180.
[12] 陈康,吴国忱.逆时偏移拉普拉斯算子滤波改进算法[J].石油地球物理勘探,2012,47(2):249-255.CHEN Kang,WU Guochen.An improved filter algorithm based on Laplace operator in reverse-time migration[J].Oil Geophysical Prospecting,2012,47(2):249-255.
[13] 唐永杰,宋桂桥,刘少勇,等.基于波长平滑算子的逆时偏移回转波假象去除方法[J].石油地球物理勘探,2018,53(1):80-86.TANG Yongjie,SONG Guiqiao,LIU Shaoyong,et al.Turning wave false image removal based on wavelength-dependent smoothing operator in reverse time migration[J].Oil Geophysical Prospecting,2018,53(1):80-86.
[14] 徐文才,李振春.各向异性介质弹性波逆时偏移[C].2014年中国地球科学联合学术年会,2014,P1162.XU Wencai,LI Zhenchun.Reverse time migration of elastic waves in anisotropic media[C].2014 China Geosciences Joint Academic Annual Meeting,2014,P1162.
[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):801-807.DU Qizhen,QIN Tong.Multicomponent prestack reverse-time migration of elastic waves in transverse isotropic medium[J].Chinese Journal of Geophysics,2009,52(3):801-807.
[16] Alkhalifah T.Acoustics approximations for process-ing in transversely isotropic media[J].Geophysics,1998,63(3):623-631.
[17] Alkhalifah T.An acoustic wave equation for aniso-tropic media[J].Geophysics,2000,65(4):1239-1250.
[18] Duveneck E,Milcik P,Bakker P M.Acoustic VTI wave equations and their application for anisotropic reverse time migration[C].SEG Technical Program Expanded Abstracts,2008,27:2186-2190.
[19] 杨富森,李振春,王小丹,等.等价各向异性介质一阶拟声波方程正演模拟及其效率分析[J].地震学报,2015,37(4):648-660.YANG Fusen,LI Zhenchun,WANG Xiaodan,et al.Equivalent anisotropic first-order pseudo-acoustic wave equations modeling and its efficiency analysis[J].Acta Seismologica Sinica,2015,37(4):648-660.
[20] Yoon K,Marfurt K J.Reverse-time migration using the Poynting vector[J].Exploration Geophysics,2006,59(1):102-107.
[21] Costa J C,Silva Neto F A,Alcabtara M R,et al.Obliquity-correction imaging condition for reverse time migration[J].Geophysics,2009,74(3):S57-S66.
[22] 李海强,杨国权,李振春,等.基于局部平面波分解的逆时偏移角道集提取方法[J].石油地球物理勘探,2017,52(6):1177-1183.LI Haiqiang,YANG Guoquan,LI Zhenchun,et al.A method for extracting angle-domain common-image gathers based on local plane wave decomposition[J].Oil Geophysical Prospecting,2017,52(6):1177-1183.
[23] Thomsen L.Weak elastic anisotropics[J].Geophy-sics,1986,51(10):1954-1966.
[24] Du X,Fletcher R,Fowler P J.A new pseudo-acoustic wave equation for VTI media[C].Extended Abstracts of 70th EAGE Conference & Exhibition,2008,1024-1028.
[25] Hestholm S.Acoustic VTI modeling using high-order finite differences[J].Geophysics,2009,74(5):T67-T73.
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