观测系统对偏移振幅和偏移噪声的影响分析

Geometry impacts on migration amplitude and migration noise

成像空间采样的不连续性会造成目的层偏移振幅的不一致,采样的不均匀性还导致偏移噪声。观测系统优化设计的主要目的即是削弱这种振幅不一致和偏移噪声。基于塔里木盆地WN区块选用的12L4S320T观测系统,本文定量分析、对比了目的层埋深、目的层倾角、接收线数、线距、点距、观测方式及其他因素对偏移振幅和偏移噪声的影响:①地震道所处子区位置的不同其偏移成像效果存在较大差别;②较浅或大倾角目的层的振幅衰减和偏移噪声更明显;③宽方位采集仅在复杂构造区或存在各向异性时才具有成像优势;④减小炮线(点)距比减小接收线(点)距对成像效果改善显著;⑤正交、斜交、砖墙等三种观测方式在相同采集参数时成像效果无明显差别。

Discontinuous spatial sampling in image domain can make the migration amplitude of targets disturbing,non-unifrm sampling lead also that irrelevant energy cannot be removed enough,and usually called by migration noise.One of the aims of geometry design is to reduce the amplitude disturbance and migration noise.Here,for the geometry of 12L4S320Tapplied in WN Block in Tarim Basin,by comparing the different imaging results in different cases,we analyze quantitatively multifactor impacts on migration amplitude and migration noise such as target depth,target dip,receiving line number,line interval,point interval,survey types and so on.The following understandings are obtained:① With different position in box, seismic imaging result in each bin show large differences.② Amplitude attenuation and migration noise are more obvious in shallow or dip target.③ Wide-azimuth acquisition has imaging advantages only in complex structural area or anisotropic medium.④ Smaller shot line(shotpoint) intervals can improve the imaging quality more than receiving line(receiver point)intervals.⑤ Orthogonal,slant and brick pattern with the same acquisition parameters give the almost same imaging results.