Technique Research On The Separation Of The Cross-well Seismic Wave Field

Cross-well seismic which can achieve the high-precision imaging of the structure and reservoir between two wells is a key technology in exploration and oil development. Cross-well seismic wave field is very rich and complex, which will increase the difficulty of the wave field separation and thus interferes with the recognition of significant wave, at the same time it also seriously affects the quality of seismic data processing. Therefore, how to distinguish and isolate the high-resolution reflected wave field from the complex cross-well seismic wave field which can be used to study the fine structure of the reservoir is the first question for geophysicists to solve.The separation of the cross-well seismic wave field can be regarded as an extension of the VSP wave field separation. It's distinct from VSP wave field separation that the cross-well seismic wave field is relatively complex and difficult to separate. This paper firstly in detail analyzed the characteristics of the cross-well seismic wave field from two aspects of kinematics and dynamics and then summarized the principle of some cross-well seismic reflection wave field separation methods which focus on SVD filtering, median filtering andτ-p filtering using VSP wave field separation and conventional seismic processing technology. On this basis, we also discussed some existing problems about the algorithm of the three methods and presented the corresponding solution. We finally implemented the algorithm by programming. Through the theoretical model and actual data calculation, the result shows that the three kinds of methods are feasible in cross-hole seismic separation application.For SVD filtering, we carried out the singular value decomposition for general real matrix mainly using Householder transforming and deformation QR method and then after that realized the filter through designing band-pass filter for singular value curve. The median filter achieved three ways for filtering:space direction median filtering, time direction median filtering and radial median filtering. To the limitation of the boundary treatment in median filter, we took zeroized edge extension processing. Linear radon transforming method is mainly used forτ-p filtering. In theτ-p domain, mouse can be used to select the filtering area whose boundary was simultaneously processed by e-exponent; furthermore, we used correlation function and velocity filtering to suppress the alias and endpoint effect in linear radon transforming and finally recovered the amplitude and energy of the post filtered data.The checking calculation of theoretical model data and practical data shows that SVD filter belong to amplitude-retaining filtering method, and the former has good effect in the separation of the wave field with higher correlation in horizontal orientation while the latter in different orientations, it basically don't change the relative relations of the separation of the wave field energy and amplitude; the Median filter has good effect in the separation of the wave field with higher correlation in different orientations,it can effectively protect the details of the signal, it's a amplitude-retaining filtering method. Theτ-p filter is not an amplitude-retaining filtering method, it's suitable for separating the linear and hyperbolic wave field with different apparent velocities, it changed the relative relations of the separation of the wave field energy and amplitude, so it needs correction of amplitude after filtering data, and then the amplitude fidelity are improved greatly.