Research On Joint Imaging Technique Of Multi-scale Seismic Data

Resolution-improving of seismic data is our focus in this paper.First,by studying the high resolution wave equation PSDM technique,a high-resolution two-way wave RTM imaging technique is formed to improve the seismic imaging accuracy.On the basis of this,using the advantages of multi-scale data like cross-well seismic,VSP and surface seismic,to study the multi-scale seismic data joint imaging technology for low,medium and high frequency components,to further enhance the resolution and accuracy of 3D seismic data,and greatly improve the resolution of small-scale geological target.Being recognized as most accurate seismic imaging technique,RTM can adapt to the complex geological structure areas with strong lateral velocity variations.However,there are still some technical bottlenecks to be solved urgently.In this paper,according to these technical choke-points and the characteristics of multi-scale seismic data,a multi-scale RTM imaging technology series is formed,core method including high precision space and time variable extrapolation algorithm,Poynting vector high-resolution imaging algorithm and Laplace filter low-frequency noise suppression method.First,the high precision space and time-variable extrapolation algorithm is adapt to different geometry including surface,VSP and cross-well seismic to meet the requirements of forward and backward extrapolation of seismic wavefields under different grid sizes and wave frequencies.Second,the Poynting vector high-resolution imaging algorithm is used to solve the multi-scale wavefield imaging of thin layers.Compared with the conventional cross-correlation imaging algorithm,the new imaging algorithm have advantages both in resolution improving and amplitude fidelity.Third,Laplace filter low-frequency noise suppression method is introduced to eliminate the migration low-frequency noise effectively and maintain high resolution characteristics simultaneously.In the prospect of joint imaging,based on two-way wave continuation RTM,by combining cross-well seismic,VSP and surface seismic data to calculate a unified imaging of continuation.The RTM continued the source wavefield forwardly first,then continued shot wavefield reversely,and extract the imaging value finally by the imaging condition selection.Both VSP,cross-well seismic,or surface seismic data,satisfy the fundmental wave equation conditions.The wave field satisfies the principle of linear stack.Based on this theory and RTM frame,combine with common shot gather array,to achieve the purpose of better imaging.Joint imaging results or single data alone can be obtained according to the needs of any combination.Joint imaging can not only maintain the accuracy of seismic data in main subsurface structures and stratigraphic interfaces,but also combine the advantages of description for miner-scale target and thin interbedded layers in cross-well seismic data,hence,improve the vertical and lateral resolution of seismic data effectively.The joint imaging technique provide a new approach for resolution-improving problem in seismic dataIn this paper,the model test of forward inversion,verified the effectiveness of joint imaging method on seismic data at different scales.The application of multi-scale joint imaging techniques in Ken 71 survey,Shengli Oilfield,a thin interbedded reservoirs of fluvial sands and shales,proved that this technique can make full use of multi-scale seismic data and improve the resolution of thin reservoirs.The field data example testifies the correctness of the multi-scale seismic data joint migration imaging theory and practical algorithm.