The Study On Method Of Layer Absorbing Parameters Extration Based On The Theory Of Seismic Wave Attenuation

With development of oil and gas exploration, more and more research has been done on the lithologic and concealed hydrocarbon reservoir rather than structural hydrocarbon reservoir. Thus studying on the seismic wave attenuation in viscoelastic medium has becoming a hotspot in recent years. Especially in the prediction of concealed lithologic natural gas reservoirs, absorption parameter was regarded as one of the most sensitive and reliable indicators. Therefore, study, evaluate and compensate for the absorption of seismic waves by underground medium is of great significance for processing prestack seismic data, improving the seismic imaging precision, explaining AVO effect logically and inversing physical attributes correctly. In recent years, earth layer absorption parameters as an intrinsical attribute of earth layer, has a significant meaning in prediction of lithology, location and range of oil and gas reservoirs.According to the development of seismic attenuation theories, and the technical requirements of natural gas prediction in real production, this thesis investigate the extraction of earth layer absorption parameters based on numerical simulation analysis the characteristic of seismic attenuation .First of all, based on the viscoelasticity medium theory, using two different ways the staggered-grid high-order finite difference method and one-way wave-equation numerical simulation method, seismic wave propagation of viscoelastic medium were simulated in this paper. From different aspect, we analyzed seismic wave characteristics and changes of seismic waves affected by earth layer absorption. Secondly, using a more advanced spectrum decomposition technology (S transform) inferred energy density function of the seismic wave propagation equation in the S domain, and analyzed the relationship between seismic wave energy, frequency and the Q value in the S domain. Combined with the numerical simulation we have conducted before, three different methods of earth layer absorption parameters extraction were proposed in time-frequency domain, and the concept of earth layer absorption comprehensive parameters were given in this paper. Moreover, in order to separate the intrinsic attenuation attribute from the decay, a Q value inversion method was put forwarded based on nonlinear waveform inversion of Bayes theory. Meanwhile, the Q value influencing factor was also added into the AVO response analysis to do the AVO-Q a nalysis in this study.Based on the above research, all the research methods and models were tested and applied to the exploration of middle-deep layer anatural gas reservoirs in an oilfield in east china. The result shows that methods of extracting attenuation parameters discussed in this paper are feasible and effective.