Study On Diffracting Objective Imaging Methods In Heterogeneous Media

With the structure, lithologic reservoir exploration and further development, the high-resolution imaging of underground sophisticated media particularly in heterogeneous media plays an important role for high-precision seismic interpretation and has become increasingly important in oil and gas exploration and development. Currently, seismic interpretation focuses on the fault, the river, the border of salt and the carbonate salt fracture-cave reservoir geological structure, and the type of the media has vertical and horizontal velocity change, relatively small-scale, irregular and heterogeneity compared and other characteristics and their seismic responses are in the seismic record rich diffraction. Conventional seismic processing techniques are mostly aimed at reflected waves, and the weak diffraction wave is generally as interference noise to process or even if the current imaging methods can make it the correct position, but also because of its energy is weak, the reflected wave energy cover it, thus reducing the resolution of diffraction imaging. Thus high-precision diffraction wave seismic imaging methods to carry out the main object of study heterogeneity target imaging emerged. Based on the response of diffraction seismic trace at different gathers, this paper analysis high-precision diffraction imaging method which aimed at heterogeneous media, thereby serving the media under complicated geological conditions of precision and complexity of seismic interpretation.This paper focuses on the field of plane-wave destruction on seperating diffraction on plane-wave domain and common offset domain. The article first describes in detail the basic principles of two-dimensional plane-wave domain seperating diffraction method basing on the geometry differences of two-dimensional plane waves diffracted wave records and reflected wave records, we use the plane-wave destruction( prediction) filtering method to seperating the diffraction. On this basis, the article analyzes the geometry differences of diffraction and reflected waves in three-dimensional plane-wave domain and that determine the feasibility to separating diffraction, and further physical model and the real data were tested and the results prove the correctness and validity of the theory. When separating diffraction by using 2D plane wave decomposition, it is a problem to separate small angle diffraction because it is similar to reflect wave and the paper introduces Li Pei method such as the proposed " two secondary separation " method, and the real data was tested. Considering the synthesis of a plane wave record low computational efficiency, due to the common offset gathers are more convenient extracted, this paper proposes the common offset gathers using Radon transform and plane-wave prediction operator combined to complete the diffracted wave separation. The method also can be compared to a plane wave filtering method to avoid the presence of a small dip to bring underestimated problem. This paper also presents a method which use singular value decomposition method to separate diffraction and image, both methods have been tested by trial numerical model to verify the correctness and validity of the two methods. Finally apply a Gaussian beam pre-stack depth migration to complete the diffraction wave imaging and enhance the resolution around the target.