Optimization Design Method Of Observation System Based On Seismic Illumination

With the development of petroleum and natural gas exploration and development to the complex structural area, the geological conditions for oil and gas exploration are becoming more and more complex. Mainly manifested as the surface high and low fluctuation, near surface loose soil which lead to excitation and receiving condition is difficult, the horizontal variation of the underground geological structure is dramatic changes, exploration targets are buried deeper, High speed layers is developing and so on. Which all rusult to seismic wave propagate complexed and Geological target image difficultly. In order to improve the reliability and efficiency of seismic data acquisition in the area of complex seismic geological condition, In recent years, geophysical workers put forward the seismic wave illumination analysis technology. Which could evaluate acquisition effect by analyzing the distribution of illumination energy of each subsurface element, and then optimize the acquisition parameters.At the same time, when the amount of the explosive of traditional single source increases to a certain degree, the seismic wave energy generated by the excitation will no longer be increased accordingly. In the Western piedmont fault area and which have many near surface scattering source and desert area which near surface soil is loose, resulted to excitation and receiving conditions are poor. It is difficult to obtain an ideal seismic data with high signal-to-noise ratio by normal source excitation. The source combination technique can realize the same phase superposition of the energy of each sub source seismic wave field in a certain direction. Which could improve the signal-to-noise ratio of seismic data and seismic wave illumination. However, in our country and abroad, the research on the optimal focus direction selection of the composite focus based on the specific target is relatively few.So this thesis is based on the previous research, the combination of source array technology, the Poynting vector and seismic wave illumination technology and we put forward to a solution for designing irregular geometry, which is based on the finite difference of two-way wave equation and source array. First, we take regular geometry to simulate, the uniformity of the illumination uniformity is determined by using the mean variance and the peak variance of the target illumination curve. Then, we excite seismic wave at the position of minimum illumination energy of target layer. When the first break arrive surface, we count the surface direction of propagation by the Poynting vector and the surface illumination energy. The main beam direction of source array is determined by the statistical result of direction. The infill location of source array is determined by the statistical result of energy. The models test results show:the method could largely improve the illumination energy of shadow zone and the illumination uniformity of target layer. This method has a certainly directed significance to acquisition system optimization of complex structure target.