Study On Methods Of Reverse Time Migration Of Multiple

When there are complex geological structures such as high-speed salt dome and high-steep structure,conventional imaging methods can not accurately image the area.Therefore,an accurate imaging algorithm for complex structures underground is urgently needed.The multiple imaging technology can make full use of the advantages of wide propagation range and small propagation angle of multiples to provide additional illumination besides primaries,and the formed imaging profile can provide more abundant information of underground structure.Compared with other migration algorithms,the reverse time migration method based on two-way wave equation can accurately image complex geological structures such as overhanging reflector and steep inclined layer,and can also image prism,scattering wave and multiples.Hence,it is of great significance to study the reverse-time migration of multiples for obtaining high-precision information of complex structures underground.In this paper,the computational accuracy,computational efficiency and noise of reverse-time migration of multiples are studied,and the following research progress has been made:The traditional primary wave forward method is modified by changing the upper boundary from the absorbing boundary to the free boundary,the forward simulation of multiples including surface multiples wave can be realized.The implementation of this method can provide data support for the later research on the multiple imaging and separation.In the research of the multiple separation,this paper realizes the multiple separation method by SRME.,and can provide technical support for obtaining the high-quality multiple imaging result.In the multiple imaging part,this paper uses reverse-time migration method to image multiples,and elaborates two different reverse-time migration methods in detail.Aiming at the problem of imaging noise in surface-related multiples imaging,this paper combines the reverse time migration method with SRME,and develops the reverse time migration of divided-order multiples.Then the de-primary imaging condition is introduced into the reverse time migration of divided-order multiples,which solves the problem of strong low-frequency noise and false imaging in the result of reverse time migration when there is a large velocity gradient in the velocity field,and achieves high precision surface multiple imaging.The numerical experiments show that the multiple imaging method can enrich the content of seismic wave imaging,increase the imaging range,coverage times and the uniformity of illumination of subsurface.