Elastic AVO Inversion

With current development of exploring technology in complex structure areas, by the understanding and recognition of AVO background, history, research of present situation and development trends, and combining with the theoretical models and the practical production, this paper mainly researched the AVO attribute parameters and lithologic parameters inversed from the prestack informations, further revealled the variable feature of lithology and pore fluid, and deeply discussed the parameter choice and its influence on the results in the process of inversion.Firstly, this paper introduced the fundamental principles and petrophysical foundation, which were very important to the interpretation of inversion results; 1 introduced the Zoeppritz equation and its different approximate equations, and discussed the precision of different approximate equations, which made bedding for the following inversion which based on the mode equation; and then, AVO response features of four types hydrocarbon bearing sands were researched; moreover, 1 discussed and researched some algorisms used in the inversion, mainly introduced linear iteration and simple genetic algorithm, and putted forward a new object function which was very effective to remove the errors caused by outliers in linear fit; the last chapter was the key of this paper, which detailedly derived the correlated formulas of attribute inversion and the development of elastic impedance formulas, analysed and discussed the parameter impact on the processing result, explained the inversion workflows of some attributes in details, beginning at geological model, synthetising CDP gathers, transformation from CDP gathers to angle gathers, trial-calculates the attributes(such as P profile, G profile, Poisson ratio differential profile, S wave profile .etc), elastic impedance and extended elastic impedance, and the outcome tallied with the geological model ext raordinary.This paper also took the prestack seismic data from some survey in SiChuan as an example, making program applying this paper's reseach thinking all alone, I treated the real data from data reading to inversing various attribute parameters and lithologic parameters, gained the same effect of logging. Analysis and treatment of real data showed that the research thinking and analytic method of this paper had certain positive significance for applying AVO technique to complex structure areas.