The Common Refection Surface Stack For Common Offset Method Research

With seismic exploration is turning to apply in area with more complex geological conformation,it is not easy any more to get satisfying image result by conventional processing method. So many new image technologies in time domain and pre-stack migration methods come out, one of which is CRS (common reflection surface) stack. The original mind of CRS stack is by Hubral in 1983. The main advantage of the CRS stack is the utility of analytical formulae that describe the kinematic reflection response of inhomogeneous media with curved interfaces based on the theory of paraxial ray. It is dependent on the near surface velocity and foreign to the macroscopic velocity model. It considers the local feature of reflector and the whole reflect of the first Fresnel zone, hence it utilizes all the information of multiple coverage reflect data effectively.The conventional Zero-Offset (ZO) CRS stack has been considered as the best ZO image method at present. The seismic reflection imaging focusing on the CRS stack is performed through the optimization of three parameters, which are emergence angleα, the curvature radius of normal-incident-point wave RN IP and the curvature radius of normal wave RN . However, imaging in complex subsurface structures as, e.g., the imaging beneath a complicated salt body, is a challenging task and the application of ZO CRS stack is often not sufficient to deliver consistent high quality imagines in such situations. Common-Offset (CO) CRS stack has been developed as an extension to the established ZO CRS stack。The number of wave parameters is five instead of three. They areβS decrised the incidence angle of the central ray at S,βGthe emergence angle at G, K1 the wavefront curvature of the emerging wave at the surface at G in CS gather, K 2 thewavefront incident at the source S in CMP gather and K 3the wavefront emerging at the receiver G. It is obviously that in case the number of parameter is increasing,it is necessary to find better matter to increase calculation efficiency.It is of interest in cases when target reflectors suffer from bad illumination by normal rays and the acquired data do not contain the necessary information for the simulation of a good ZO section.Using CO CRS stack, optional Finite-Offset stack sections can be obtained and this procedure reduces the number of traces used in the migration and may significantly increase the signal-to-noise ratio within the prestack data volume. Application on model data reveals that comparing with the image section by the conventional ZO CRS stack, the image section by CO CRS stack is much better in the aspect of signal-to-noise ration and the continuity of reflection event.