摘要
将多次波转换成反射波并按传统反射波偏移算法成像,是多次波成像的一种方法.聚焦变换能准确的将多次波转换为纵向分辨率更高的新波场记录,其中一阶多次波转换为反射波.本文对聚焦变换提出了两点改进:1)提出局部聚焦变换,以减小存储量和计算量,增强该方法对检波点随炮点移动的采集数据的适应性;2)引入加权矩阵,理论上证明原始记录的炮点比检波点稀疏时,共检波点道集域的局部聚焦变换可以将多次波准确转换成炮点与检波点有相同采样频率的新波场记录.本文在第一个数值实验中对比了对包含反射波与多次波的原始记录做局部聚焦变换和直接对预测的多次波做局部聚焦变换两种方案,验证了第二种方案转换得到的波场记录信噪比更高且避免了第一个方案中切聚焦点这项比较繁杂的工作.第二个数值实验表明:在炮点采样较为稀疏时,该方法能有效的将一阶多次波转换成反射波;转换的反射波能提供更丰富的波场信息,成像结果更均衡、在局部有更高的信噪比,以及较高的纵向分辨率.
Surface-related multiples penetrate into the subsurface several times and contain abundant reflection information of small angles.Compared with primaries,they sometimes can provide higher fold and better illumination for subsurface.Instead of trashing multiples as noises during the seismic data processing,nowadays,a lot of methods have been proposed to image multiples.Conventional migration methods have been modified for directly imaging multiples,e.g.,Kirchhoff migration of multiples,wave equation migration of multiples,or reverse-time migration（RTM）of multiples.Alternatively,the linear two-step procedures can be utilized for imaging multiples.Primaries can be extracted from multiples based on seismic interferometry or focal transformation,and then imaged by utilizing conventional migration methods.However,most methods for imaging multiples would generate so many artifacts due to the undesired interactions between seismic-events（i.e.primaries and different-order multiples）,which are hard to be attenuated and seriously pollute the true-image.Moreover,the least-squares based focal transformation can transform first-order multiples into primaries,second-order multiples into first-order multiples,etc.,with few noises generated.Multiples focal-transformed from higher-order multiples can be eliminated by surface-related multiples elimination（SRME）.And then,primaries focal-transformed from first-order multiples can be imaged by any conventional migration methods,and we call the procedures focal transformation imaging of first-order multiples.The focal transformation is proposed by Berkhout and Verschuur,which is developed from SRME.Primaries are once subsurface response of sources,surface-related multiples include different-orders,and the raw data contain primaries and surface-related multiples.Focal transformation is manipulated with several matrices that contain the full data of mono-frequency,one column stores one shot gather or one common-receiver gather.Primaries need to be estimated prior to focal tra
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2015年第6期1985-1997,共13页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(41374138)
国家油气重大专项(2011ZX05008-006)
中国科学院战略性先导科技专项(B类)(XDB01020300)联合资助
关键词
聚焦变换
多次波成像
多次波消除
Focal transformation
Imaging of multiples
Multiples elimination
