Seismic Multiple Illumination And Research Of Seismic Acquisition Methods In The Complex Geological Regions

Domestic demand for energy is more and more tensely along with the rapid development of the national economy.In order to increase the energy reserves, the strategic center of the sei-smic exploration has been moved from the eastern plain areas to the Midwest mountain and pl-ateau regions. Some big oilfields have been successively found in these areas, rich in oil and gas. such as Kelamayi oilfield,Talim oilfield and Tuha oil field. But in these areas, it is different from the eastern regions with the complex geological structure. Therefore, the acquisition methods based on CMP are not suitable for complicated geological conditions. Seismic exploration has large investment risk for the new exploraion areas.In order to improve the economic benefit,some new exploration techologies will be used to study and analysis the collection parameters in desperate need, which will optimize the field collection observation system and improve the accuracy of exploration targets and provide theoretical guidance and technical support for searching the new concealed reservoirs.In the field seismic exploration early.it can be simulated for the geological structure parameters of argumentation,such as seismic folds,offset and recevers indoor simulation.Therefore, it can modify the gathering parameters and increase the exploration benefit by the conclusion obtained in exploration simulation.It is simple to establish the layered media on the basis of the conventional modeling technology and it is suitable for the eastern plain area but not for the Midwest plateau due to the complicated geological structure.In this thesis, it will be introduced a new two-dimensional modeling method by studying the conventional modeling.its basic elements are dot,broken and surface. The new modeling method is successful in the sim-ulation of the overthrust fault in the western complex geological structure.Because the computer hardware restrictions and the man-made boundary issue.the wave equation modeling algorithm is different from the wild seismic exploration. At the same time,we must study the source in the indoor simulation. In order to discrete the continuous problem, scholars at home and abroad have received many achievements in the process of studying the wave propagation. There are some good effect in the studying boundary problem.such as fully absorting boundary. Many wavelet function have been successively developed by the research and analysis of the source characteristics. One of the famous wavelets is Ricker wavelet, and it has been widely used in the wave field sim-ulation with the high resolution wade frequency characteristics.The forward modeling is a useful tool in the study of the wave field characteristic. There are two methods to simulate the seismic wave propagation.geometric ray method and wave equation method. Geometric ray method simulate the seismic wave propagation on the base of the high frequency approximation, it mainly reflects the wave of kinematic features, and wave equation method can not only provide the wave of kinematic features but also reflects the wave of the kinetic parameters. Therefore,the wave equation method has been applied extensiveely in the forward modeling. Along with the rapid development of the computer software and hardware, the numerical simulation technology has been used in many fields. In the wave equation simulation technology,there are three numerical simulation methods, including finite element method,the method of pseudo-spectral and finite difference method. Because of the simple and simulating various geological structure,the finite difference method has been used widely. In the process of studing the wave propagation with the discretization problem, the finite difference operators has been deduced, at the same time, its stability,convergence and frequency dispersion relationnship have been studied too. In the seismic exploration, the physical properties of the rocks are studied by the artificial mechanical vibration of the medium when the seismic wave propagats. The anisotropic medium namely transverse isotropic media exists widely in the lithosphere. The finite difference formula,describing the movement of the elastic medium, has been established from the broad Hooker law.and the seismic illumination simulation with finite difference operators began laterly.ln this text,it is concluded that it is very helpful to improve the field exploration by simulating the illumination of the compress waves and shear waves (it refers to convert sv waves here).The seismic illumination can simulate the field seismic exploration collecting methods, optimize the designation of the system, so it can reduce the risk of investment and improve the economic benefit. Therefore, it are used as a kind of evaluation methods of field collection usually. The seismic illumination are influenced by the seismic exploration gathering parameters.such as the source,the arrangement of receiving mode,the distance between the recevers and the subsurface geologic structure.Firstly,the ray tracing was used in the seismic research method for the illumination.and this kind of method works well in the horizontal layer structure of geological model, but does bad in the complicated geological model due to the defects of ray tracing law itself. Because of adapting to the complicated geological model, the wave equation method can provide more information to study of the medium physical parameter in the wave field. By establishing the complicated geological model and underground concealed deposits of oil and gas with differrent geological environment, we can obtain the conclusion of the illumination, optimizing the acquisition method, increasing explorat-ion precision.So we can establish the optimizated acquisition system based on exploration targets truly,with which to improve the economic benefit with theoretical guidance and technical support.The seismic denoising technology is important in the process of the seismic exploration, it plays an important role to obtain the true imaging underground geologic structure, especially in the complicated geological conditions,the influence of the long wavelength and the short wavelength statics problem is important in the process of the seismic data.In this thesis,I have gotten the achievements in studing the seismic illumination and processing the seismic data under the complex geological conditions and the experience to study of the complex ge-ological region.