叠前时间偏移解析速度分析  

Analytic velocity analysis in prestack time migration.

作　　者：徐基祥[1] 崔化娟[1] 

机构地区：[1]中国石油勘探开发研究院

出　　处：《石油地球物理勘探》2004年第4期388-393,405,共7页Oil Geophysical Prospecting

摘　　要：常规叠后地震速度分析通常基于三个假设条件,即横向速度均匀、小炮检距、水平反射层。这类假设不符合我国地质构造的特点。为此,本文提出叠前时间偏移解析速度分析方法。该法通过研究共成像点道集上同相轴的深度随炮检距的变化规律,得出以下结论1同相轴的深距曲线为抛物线;2同相轴的深度误差与速度的相对误差成正比;3同相轴的深度误差与真深度成反比;4同相轴平直时,成像深度为真深度。其主要实现步骤为首先利用三次叠前时间偏移道集上同相轴的时差,解析求取这种时差(或称延迟)为零时所对应的速度,此速度即为所需的成像速度;然后利用此速度进行叠前时间偏移处理,通过对实际资料处理结果的观察可以看出,该法简便实用、效果明显。Petroleum Exploration & Development Science Institute,Beijing City,100083,China Abstract:Common poststack seismic velocity analysis is on the basis of three hypotheses: uniform lateral velocity,small offset and horizontal reflector, which is inconsistent with the feature of geologic sedimentary structure in China Abstract:.Therefore,the paper presented the method of analytic velocity analysis in prestack time migration.By studying the rule of variation of event depth versus offset on common imaging point gathers,the method can result in following conclusions: ①the depth ditance curves of events are hyperbolic;②the errors of event depth are directly related to relative errors of velocity;③the errors of event depth are inversely related to true depth;④imaging velocities are true velocities when events are flat.The main implementing steps are: using moveout of events on third order prestack time migrated gathers to analytically compute the velocities when the moveout (or called as delay)is zero,which are needed imaging velocities;then using these velocities for prestack time migration.The method is used for practical data processing,it's seen from the results that the method is simple and practical and effects are evident.

关 键 词：同相轴 叠前时间偏移 深度误差 速度分析 炮检距 时差 地震速度 解析 像点 抛物线 

分 类 号：TE132.1[石油与天然气工程—油气勘探] P631[天文地球—地质矿产勘探]