基于时间窗互相关成像条件的GPR逆时偏移成像
|
摘要
针对基于互相关成像条件的探地雷达(GPR)逆时偏移在地下介质的非反射点处易产生强噪声的不足,根据偏移速度模型中每个成像点的主反射时间,设计一个时间窗函数以压制时间窗外的噪声干扰,提出了一种基于时间窗互相关成像条件的GPR逆时偏移算法。其中,时域有限差分法(FDTD)用于计算正传和反传电磁波场,时间窗内正传与反传电磁波场的归一化互相关计算结果作为权系数作用于基于归一化互相关成像条件的GPR逆时偏移剖面,拉普拉斯滤波用于压制低频噪声。在此基础上,编制了基于时间窗互相关成像条件的GPR逆时偏移程序,利用该程序对两个典型的GPR模型的正演数据和实测数据进行计算,结果表明:相比于归一化互相关成像条件的逆时偏移结果,基于时间窗互相关成像条件的GPR逆时偏移剖面的低频噪声更弱、杂波干扰更小、空间分辨率更高、成像精度更好。
As ground-penetrating radar(GPR) reverse time migration based on cross-correlation imaging condition, it is easy to generate strong noise in the reverse time migration profile of GPR at the non-reflection points of subsurface media. In this study, a time window function is designed and applied to the incident wave field and scattering wave field for each imaging point, to strengthen the correlation of the wave fields in the time domain. The finite difference time domain method(FDTD) is used to calculate the forward and backward electromagnetic wave fields. The normalized cross-correlation results of the forward and backward electromagnetic wave fields in the time window are used as the weight coefficients for normalized cross-correlation imaging. Laplacian filtering is used to suppress low-frequency noise. On this basis, a GPR inverse time migration program based on time window cross-correlation imaging condition was developed. Simulated data of two typical GPR models and observed data were calculated, and GPR inverse time migration was performed and compared with the normalized cross-correlation imaging condition. The results show that the GPR reverse-time migration imaging section based on the time-window cross-correlation imaging condition has low-frequency noise, less clutter, better spatial resolution and higher imaging accuracy, than that in the normalized cross-correlation imaging condition.
As ground-penetrating radar(GPR) reverse time migration based on cross-correlation imaging condition, it is easy to generate strong noise in the reverse time migration profile of GPR at the non-reflection points of subsurface media. In this study, a time window function is designed and applied to the incident wave field and scattering wave field for each imaging point, to strengthen the correlation of the wave fields in the time domain. The finite difference time domain method(FDTD) is used to calculate the forward and backward electromagnetic wave fields. The normalized cross-correlation results of the forward and backward electromagnetic wave fields in the time window are used as the weight coefficients for normalized cross-correlation imaging. Laplacian filtering is used to suppress low-frequency noise. On this basis, a GPR inverse time migration program based on time window cross-correlation imaging condition was developed. Simulated data of two typical GPR models and observed data were calculated, and GPR inverse time migration was performed and compared with the normalized cross-correlation imaging condition. The results show that the GPR reverse-time migration imaging section based on the time-window cross-correlation imaging condition has low-frequency noise, less clutter, better spatial resolution and higher imaging accuracy, than that in the normalized cross-correlation imaging condition.
引文
[1]杨修超,林年添,张栋,等.利用全波形反演提高逆时偏移成像的精度[J].地球物理学进展,2016,31(3):1257-1261.
[2]戴前伟,冯德山,何继善.Kirchhoff 偏移法在探地雷达正演图像处理中的应用[J].地球物理学进展,2005,20(3):849-853.
[3]董臣强,谭明友,张明振,等.Kirchhoff 积分法叠前深度偏移技术在孤岛地区的应用[J].石油地球物理勘探,2002,37(2):180-184.
[4]Bitri A,Grandjean G.Frequency-wavenumber modelling and migration of 2D GPR data in moderately heterogeneous dispersive media[J].Geophysical Prospecting,1998,46:287-301.
[5]李文忠.F-K 偏移技术在地质雷达资料处理方面的应用[J].物探化探计算技术,1998,20(3):280-283.
[6]戴前伟,张彬,冯德山.探地雷达各向异性介质有限差分偏移线性变换[J].中南大学学报(自然科学版),2012,43(5):1814-1820.
[7]冯德山,戴前伟.基于小波多分辨探地雷达三维正演模拟及偏移处理[J].中南大学学报 (自然科学版),2007,38(4):758-763.
[8]陈德鹏,戴前伟,冯德山,等.基于归一化互相关成像条件的GPR逆时偏移成像[J].中南大学学报(自然科学版),2018,49(5):1221-1227.
[9]Fisher E,McMechan G A,Annan A P,et al.Examples of reverse-time migration of single-channel,ground-penetrating radar profiles[J].Geophysics,1992,57(4):577-586.
[10]傅磊,刘四新,刘澜波,等.机载探地雷达数值模拟及逆时偏移成像[J].地球物理学报,2014,57(5):1636-1646.
[11]王敏玲,王洪华,张智,等.基于激发振幅成像条件的探地雷达逆时偏移成像[J].地球物理学报,2018,61(8):3435-3445.
[12]Bradford J H.Reverse-time prestack depth migration of GPR data from topography for amplitude reconstruction in complex environments[J].Journal of Earth Science,2015,26(6):791-798.
[13]Lu X L,Qian R Y,Liu L B.Ground-penetrating radar finite-difference reverse time migration from irregular surface by flattening surface topography[C]//2016 16th International Conference on Ground Penetrating Radar(GPR).Hong Kong,2016:1-5.
[14]朱尉强,黄清华.探地雷达衰减补偿逆时偏移成像方法[J].地球物理学报,2016,59(10):3909-3916.
[15]杨海宁.钻孔测井雷达信号处理技术研究[D].成都:电子科技大学,2016.
[16]刘红伟,刘洪,邹振,等.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.
[17]康玮,程玖兵.叠前逆时偏移假象去除方法[J].地球物理学进展,2012,27(3):1163-1172.
[18]石颖,王建民,田东升,等.应用于叠前逆时偏移的拉普拉斯算子去噪法[J].大庆石油地质与开发,2012,31(5):154-157.
[19]张智,刘有山,徐涛,等.弹性波逆时偏移中的稳定激发振幅成像条件[J].地球物理学报,2013,56(10):3523-3533.
[20]徐兴荣,王宇超,胡自多,等.基于波场分离的逆时偏移成像条件研究及在准噶尔盆地的应用[J].天然气地球科学,2012,23(3):602-606.
[21]丁亮,刘洋.基于归一化波场拆分互相关成像条件的叠前逆时偏移方法[J].石油地球物理勘探,2012,47(3):411-417.
[22]Yang H N,Li T J,Li N,et al.Time-gating-based time reversal imaging for impulse borehole radar in layered media[J].IEEE Transactions on Geoscience and Remote Sensing,2016,54(5):2695-2705.
[23]Claerbout J F,Johnson A G.Extrapolation of time-dependent waveforms along their path of propagation[J].Geophysical Journal Royal Astronomical Society,1971,26:285-293.
[24]Schleicher J,Costa J C,Novais A.A comparison of imaging conditions for wave-equation shot-profile migration[J].Geophysics,2008,73(6):S219-S227.
[2]戴前伟,冯德山,何继善.Kirchhoff 偏移法在探地雷达正演图像处理中的应用[J].地球物理学进展,2005,20(3):849-853.
[3]董臣强,谭明友,张明振,等.Kirchhoff 积分法叠前深度偏移技术在孤岛地区的应用[J].石油地球物理勘探,2002,37(2):180-184.
[4]Bitri A,Grandjean G.Frequency-wavenumber modelling and migration of 2D GPR data in moderately heterogeneous dispersive media[J].Geophysical Prospecting,1998,46:287-301.
[5]李文忠.F-K 偏移技术在地质雷达资料处理方面的应用[J].物探化探计算技术,1998,20(3):280-283.
[6]戴前伟,张彬,冯德山.探地雷达各向异性介质有限差分偏移线性变换[J].中南大学学报(自然科学版),2012,43(5):1814-1820.
[7]冯德山,戴前伟.基于小波多分辨探地雷达三维正演模拟及偏移处理[J].中南大学学报 (自然科学版),2007,38(4):758-763.
[8]陈德鹏,戴前伟,冯德山,等.基于归一化互相关成像条件的GPR逆时偏移成像[J].中南大学学报(自然科学版),2018,49(5):1221-1227.
[9]Fisher E,McMechan G A,Annan A P,et al.Examples of reverse-time migration of single-channel,ground-penetrating radar profiles[J].Geophysics,1992,57(4):577-586.
[10]傅磊,刘四新,刘澜波,等.机载探地雷达数值模拟及逆时偏移成像[J].地球物理学报,2014,57(5):1636-1646.
[11]王敏玲,王洪华,张智,等.基于激发振幅成像条件的探地雷达逆时偏移成像[J].地球物理学报,2018,61(8):3435-3445.
[12]Bradford J H.Reverse-time prestack depth migration of GPR data from topography for amplitude reconstruction in complex environments[J].Journal of Earth Science,2015,26(6):791-798.
[13]Lu X L,Qian R Y,Liu L B.Ground-penetrating radar finite-difference reverse time migration from irregular surface by flattening surface topography[C]//2016 16th International Conference on Ground Penetrating Radar(GPR).Hong Kong,2016:1-5.
[14]朱尉强,黄清华.探地雷达衰减补偿逆时偏移成像方法[J].地球物理学报,2016,59(10):3909-3916.
[15]杨海宁.钻孔测井雷达信号处理技术研究[D].成都:电子科技大学,2016.
[16]刘红伟,刘洪,邹振,等.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.
[17]康玮,程玖兵.叠前逆时偏移假象去除方法[J].地球物理学进展,2012,27(3):1163-1172.
[18]石颖,王建民,田东升,等.应用于叠前逆时偏移的拉普拉斯算子去噪法[J].大庆石油地质与开发,2012,31(5):154-157.
[19]张智,刘有山,徐涛,等.弹性波逆时偏移中的稳定激发振幅成像条件[J].地球物理学报,2013,56(10):3523-3533.
[20]徐兴荣,王宇超,胡自多,等.基于波场分离的逆时偏移成像条件研究及在准噶尔盆地的应用[J].天然气地球科学,2012,23(3):602-606.
[21]丁亮,刘洋.基于归一化波场拆分互相关成像条件的叠前逆时偏移方法[J].石油地球物理勘探,2012,47(3):411-417.
[22]Yang H N,Li T J,Li N,et al.Time-gating-based time reversal imaging for impulse borehole radar in layered media[J].IEEE Transactions on Geoscience and Remote Sensing,2016,54(5):2695-2705.
[23]Claerbout J F,Johnson A G.Extrapolation of time-dependent waveforms along their path of propagation[J].Geophysical Journal Royal Astronomical Society,1971,26:285-293.
[24]Schleicher J,Costa J C,Novais A.A comparison of imaging conditions for wave-equation shot-profile migration[J].Geophysics,2008,73(6):S219-S227.