地层倾角对转换波动校速度分析的影响
|
摘要
动校正速度的求取是三维转换波数据处理的重要环节,其精度高低对转换波的叠加成像质量影响很大。理论上转换波的速度求取受包括界面倾角在内的多种因素影响,但实际应用时这些因素往往被忽略。为证明倾角对动校速度的影响程度,依据前人的研究成果,模拟倾斜地层计算了不同倾角条件下二维测线CCP道集、三维全方位CCP道集PS波动校正速度,并对由不同倾角引起的计算精度差异进行了研究。研究结果表明,对于二维转换波CCP道集,界面倾角不同,动校拉平的速度会差别较大,即使如此也总能实现很大倾角范围内的CCP道集的同相叠加,获得较好的成像质量;对于三维全方位CCP道集,当界面倾角超过一定范围,无论怎样进行精细扫描,得到的都只能是适合特定方位的速度,无法得到适合任意方位的动校扫描速度,随着界面倾角的减小,利用速度扫描的办法可以在一定的偏移距范围内将来自不同方位的记录较平,界面倾角越小,可以校平的偏移距越大;另外由于道集内的地震记录依赖视倾角的动校正速度,在反射界面倾斜的情况下,方位不同,动校正速度不同,致使二维反射PS波资料往往比三维反射PS波资料容易叠加成像。
Seeking for dynamic corrected velocity is an important link in 3D converted wave data processing.Its accuracy has major impact on the quality of converted wave stack imaging.Theoretically,the seeking for converted velocity is impacted by multiple factors including interface dip angle,however,these factors are usually ignored in practices.Based on forerunners' studies,designed model has calculated 2D line CCP trace gather,3D omni-directional CCP trace gather P and S wave dynamic corrected velocity under different dip angles,and studied differences of calculated accuracy because of dip angle discrepancy.Pointed out to 2D converted wave CCP trace gather,under different interface dip angles,dynamic correction flattened velocities have major distinction,even if under the large dip angle range can also realize CCP trace gather in-phase stacking and get better image quality,as for 3D omni-directional CCP trace gather,when interface dip angles surpass a certain range,no matter how to carry out refined scanning,can get only velocities adaptable to a specific direction,unavailable to get dynamic corrected velocities adaptable to any direction.Along with interface dip angle decreasing,to use velocity scanning can flatten records from different direction in a certain offset range,the smaller the interface dip angle,the larger the offset range.In addition,seismic records in trace gather rely on apparent dip angle dynamic corrected velocity,when the reflection interface is oblique,under different directions have different dynamic corrected velocities,result in 2D reflection P and S waves data stack imaging is easier than that of 3D reflection P and S waves data.
Seeking for dynamic corrected velocity is an important link in 3D converted wave data processing.Its accuracy has major impact on the quality of converted wave stack imaging.Theoretically,the seeking for converted velocity is impacted by multiple factors including interface dip angle,however,these factors are usually ignored in practices.Based on forerunners' studies,designed model has calculated 2D line CCP trace gather,3D omni-directional CCP trace gather P and S wave dynamic corrected velocity under different dip angles,and studied differences of calculated accuracy because of dip angle discrepancy.Pointed out to 2D converted wave CCP trace gather,under different interface dip angles,dynamic correction flattened velocities have major distinction,even if under the large dip angle range can also realize CCP trace gather in-phase stacking and get better image quality,as for 3D omni-directional CCP trace gather,when interface dip angles surpass a certain range,no matter how to carry out refined scanning,can get only velocities adaptable to a specific direction,unavailable to get dynamic corrected velocities adaptable to any direction.Along with interface dip angle decreasing,to use velocity scanning can flatten records from different direction in a certain offset range,the smaller the interface dip angle,the larger the offset range.In addition,seismic records in trace gather rely on apparent dip angle dynamic corrected velocity,when the reflection interface is oblique,under different directions have different dynamic corrected velocities,result in 2D reflection P and S waves data stack imaging is easier than that of 3D reflection P and S waves data.
引文
[1]T essmer G,Behle,A.Common reflection point data-stacking technique for converted wave[J].Geophysics,Prospecting,1988,36:671-688.
[2]Thomsen L.Converted-wave reflection seismology over inhomogenous,anisotro-py media[J].Geophysics,1999,64:678-690.
[3]姚陈.倾角CDP和倾角CCP叠加[M]//中国地球物理.长春:吉林大学出版社,2005:556.
[4]于光明,姚陈.倾斜CCP道集抽取方法及影响因素分析[J].煤田地质与勘探,2007,35(4):65-69.
[5]马社坤,夏青,徐奭,等.山地大倾角地层三维地震资料处理研究[J].中国煤田地质,2005,17(04).
[6]姚陈,余光明,蔡明刚,等.三维倾斜界面反射P波和PS波正演计算[G]//中国地球物理学会.中国地球物理学会第十八届年会论文集,2002.
[7]肖建华,胡宗正,唐德林,等.山区大倾角地层地震资料的动静校正及叠加问题[J].中国煤田地质,2003,15(05).
[2]Thomsen L.Converted-wave reflection seismology over inhomogenous,anisotro-py media[J].Geophysics,1999,64:678-690.
[3]姚陈.倾角CDP和倾角CCP叠加[M]//中国地球物理.长春:吉林大学出版社,2005:556.
[4]于光明,姚陈.倾斜CCP道集抽取方法及影响因素分析[J].煤田地质与勘探,2007,35(4):65-69.
[5]马社坤,夏青,徐奭,等.山地大倾角地层三维地震资料处理研究[J].中国煤田地质,2005,17(04).
[6]姚陈,余光明,蔡明刚,等.三维倾斜界面反射P波和PS波正演计算[G]//中国地球物理学会.中国地球物理学会第十八届年会论文集,2002.
[7]肖建华,胡宗正,唐德林,等.山区大倾角地层地震资料的动静校正及叠加问题[J].中国煤田地质,2003,15(05).
版权所有：© 2023 中国地质图书馆 中国地质调查局地学文献中心