The Amplitude Compensation Method Research On Post-stack Seismic Data

In the background that the oil and gas exploration degree is deepening both at home and abroad and the comprehensive geological interpretation method which makes seismic data as the main interpretation platform is widely used, the relative amplitude preservation of post-stack seismic data is particularly important. Affected by a series of high impedance special lithologic bodies such as igneous rock, carbonate rock and so on, the seismic reflection characteristics of its underlying formation distorts, especially amplitude attenuation is serious, all of above have a serious impact for the 2d structure interpretation, the track of layer and the follow-up work such as reservoir prediction. Although the existing pre-stack or post-stack seismic data processing technology can make the corresponding processing and improve the quality of imaging, in some areas, it makes the technology cannot process underlying formation for all special lithologicbodies and the Abnormal amplitude attenuation of some special lithlolgic bodies underlying formation is still there because the size and distribution of special lithologic bodies are not regular.In order to solve the problem, firstly the 2d geological model that igneous rock invades the formation is built according to the actual situation and the 2d post-stack seismic section is calculated by using elastic wave equation; on this basis, with the contrast of amplitude spectrum in frequency domain between seismic traces in abnormal amplitude attenuation areas of igneous rock underling formation and normal seismic traces in the same formation outside the range of igneous rock, the amplitude compensation factor is calculated by analyzing amplitude spectrum of them; then the boundary of abnormal amplitude attenuation areas and the transitional belt of amplitude attenuation near the boundary are determined by the contrast of amplitude spectrum difference factors of neighbouring seismic traces in 2d seismic section which are calculated by using least squares method; finally the effective amplitude compensation processing is made for seismic section by using corresponding amplitude compensation factors and amplitude difference factors in different areas(the transitional belt and attenuation belt). In view of the actual 2d post-stack seismic data, with the contrast of amplitude spectrum in frequency domain between normal amplitude seismic traces and abnormal amplitude attenuation seismic traces for theory basis, this paper calculates the true formation reflection coefficient using logging data which is in amplitude attenuation areas and then extracts the average seismic wavelet combining with the true formation reflection coefficient and seismic traces near the borehole outside the special lithologic bodies. Then calculates the amplitude compensation factor by analyzing amplitude spectrum of synthetic seismic record traces(normal amplitude seismic traces) calculated by combining with the true formation reflection coefficient and the average seismic wavelet and seismic traces near the borehole in the areas of abnormal amplitude attenuation in frequency domain with least squares method. Finally, the effective amplitude compensation processing is made for seismic data in the areas of abnormal amplitude attenuationaccording to the same method of 2d forward model.In abnormal amplitude attenuation areas of 3d post-stack seismic data, this paper calculates the true formation reflection coefficient using logging data which is in amplitude attenuation areas and then extracts the average seismic wavelet combining with the true formation reflection coefficient and seismic traces near the borehole outside the special lithologic bodies. Then calculates the amplitude compensation factor by analyzing amplitude spectrum of synthetic seismic record traces(normal amplitude seismic traces) calculated by combining with the true formation reflection coefficient and the average seismic wavelet and seismic traces near the borehole in the areas of abnormal amplitude attenuation in frequency domain with least squares method. Then the areal distribution of amplitude compensation factor is calculated by combining with the method of Kriging which belongs to geostatistic. Finally, on the basis of 2d survey line, the effective amplitude compensation processing is made for 3d post-stack seismic data in the areas of abnormal amplitude attenuationone by one according to the same method of 2d post-stack seismic data.The inspection of actual seismic attribute extraction and the corresponding sedimentary facies analysis show that the amplitude compensation results are accurate and reliable using this method, the method reduces the workload and improves the flexibility and efficiency of the process compared with the pre-stack seismic data imaging processing technology. On this basis the method helps carrying on the effective well placement and meanwhile promotes the development of oil and gas explorationin the direction of the accurate and efficient.