基于等效参数的三维复杂地表叠前偏移成像方法研究

The biggest difficulty of seismic exploration often comes from the complex surface. For migration imaging, it not only affects the travel time, but also attenuates amplitude and changes phase of seismic waves. Because the S/N of seismic data recorded from complex areas is always low, and it is very difficult to obtain the accurate models of migration parameters (such as velocity and quality factor Q), which makes those accurate imaging methods based on wave equation such as reverse time migration unpractical. In the previous study, we have proposed a pre-stack time migration scheme from topography by introducing two effective velocity parameters. This project aims to further develop a directly pre-stack Q migration method based on the introduced effective Q parameters to solve the problem of absorption and attenuation under complex surface. Similar to the building of the effective velocity models, we intend to develop a new scheme of estimating effective Q fields by reflection seismic data. Considering the factors of low S/N data and amplified noise by Q compensation, we plan to implement dip-angle domain stationary-phase in the process of migration to suppress noises. This study can build the migration velocity fields as well as Q fields, and obtain the high resolution migration images directly from complex topography, that could provide new ideas for seismic imaging of low S/N data sets recorded on complex surface, and has important research value and application prospect.

地震勘探面临的最大困难往往来自复杂地表，对于偏移成像而言不仅影响地震波的走时同时也衰减幅值和改变相位。由于三维复杂地表条件下采集地震数据的信噪比较低，获得精确的参数（如速度和品质因子Q）模型非常困难，基于波动方程的逆时偏移等高精度成像方法难以实际应用。针对三维复杂地表条件下的偏移成像问题，我们已经研究了通过引入等效速度能自主建立速度模型的起伏地表直接叠前偏移方法，本申请项目拟进一步发展一种基于等效Q值的三维复杂地表黏弹性偏移成像方法，解决复杂地表条件下的吸收衰减问题。类似于等效速度场的建立，本研究拟发展通过反射地震数据建立等效Q值场的方法；考虑到低信噪比数据和Q补偿放大噪音的问题，拟结合倾角域稳相在偏移过程中压制噪音。该方法可自主完成偏移速度和Q值建模，从真地表直接偏移得到高分辨率的地震成像结果，可为我国复杂山地低信噪比数据地震成像提供新思路，具有重要的研究价值和应用前景。

复杂地表给地震数据的采集和处理带来了很大困难。针对复杂近地表条件下的地震成像问题，项目发展了基于等效参数的三维起伏地表高分辨率直接叠前偏移成像方法和技术，对于解决我国西部崎岖山地及黄土塬地区的地震成像具有重要的实际应用价值。项目取得的主要进展包括：1）发展了一种基于近地表等效Q值的补偿吸收衰减的起伏地表直接叠前时间偏移方法和技术；2）实现了三维起伏地表直接生成倾角道集的方法并应用到了近地表吸收衰减补偿的噪音压制；3）发展了一种基于双等效Q值的起伏地表Q偏移地震成像方法与技术。本项目发展的整套方法技术可以适应三维复杂地表的高效自主偏移参数建模和高分辨率叠前偏移成像。项目相关的研究成果以第一资助发表在了勘探地球物理权威期刊《GEOPHYSICS》上，同时申报了2项国家发明专利。