【作者】 曹守山；

【导师】 贺振华； 黄德济；

【作者基本信息】 成都理工大学 ， 应用地球物理， 2008， 硕士

【摘要】 目前,常规的地震资料处理一般采用叠后偏移,它只能解决反射层归位和绕射波收敛,而不能解决倾斜界面的非共反射点叠加问题。而改进的方法是叠前部分偏移,它消除了地层倾角因素的影响,改善了CMP叠加效果。但DMO只是部分叠加,用DMO后的CMP道集做速度分析仍然受到速度分析点正下方周围倾斜反射层的影响,使速度分析结果受影响。因此,必须采用叠前深度偏移成像技术。本文首先阐述了偏移的概念、偏移的基本原理等内容,对克希霍夫积分法和波动方程这两种叠前深度偏移的方法进行了详细的介绍,并简单的介绍了与克希霍夫积分法旅行时计算相关的射线追踪理论。最后通过Marmousi复杂断层模型、SEG盐丘模型和另外两个数据模型叠前深度偏移成象试验比较,得出克希霍夫积分法叠前深度偏移方法具有灵活的目标处理能力、可接受的成像效果、极高的计算效率。但该方法的缺陷是成像精度低、容易产生假频、振幅不保真、偏移孔径选择困难和多走时问题。而波动方程叠前深度偏移成像精度高、振幅保真、能体现地震波的动力学特征,但是波动方程的计算效率是目前急需解决的问题。另外通过数据处理,也得到了以下的几点认识和结论:1、叠前时间偏移并不是一个独立的处理过程,其成像效果与基础处理密不可分。2、速度场是直接影响偏移结果的关键,合理的、接近地质真实的、高精度的速度模型是叠前偏移获得高质量效果的前提。叠前偏移除了其算法本身外,剩下的工作主要就是建立速度模型。建立速度模型是一个复杂而费时的迭代过程。3、对偏移孔径的实验可以在偏移质量和偏移效率中寻找到最佳的结合点。更多还原

【Abstract】 At present, the routine seismic data processing is poststack migration, it just can not moves dipping reflector to their true subsurface positions and collapses diffractions. The improved way is prestack partial migration. It can avoid the influence of tilted stratum and yield an improved stacked section. But velocity analysis using CMP gathers after DMO is not exact. So, it must use prestack migration imaging technology.Firstly, the paper shows the migration concepts, the basic theory of migration and so on, then I introduce two kinds of prestack migration methods which are kirchhoff integration migration and wave equation migration, also introduced to the ray tracing theory which related to calculate of travel time. Finally, The Marmousi complex fault model, the SEG salt dome model and the other two data model pre-stack depth migration imaging test show that Kirchhoff integration pre-stack depth migration method is flexible handling capacity of the target, acceptable The imaging results, high efficiency. The wave equation pre-stack depth migration can provide high precision, amplitude fidelity, but the time cost of calculation is expensive. In addition, through participating in this processing project, I summarize some recognitions and conclusions:1.Prestack time migration is not an independent process,and its imaging result is tightly related with the basic process.2.Velocity filed is a key aspect which directly affects migration result. Rational and high precise velocity model closed to the real geology is precondition to get high quality by prestack depth migration.3.We can tack both the migration quality and migration efficiency into account and choose the best value of migration aperture in the experiment.更多还原