Research On Methods Of Prestack 3-term Simultaneous Inversion And Software Module Design

Amplitude Versus Offset(AVO) inversion identifies lithology parameters and predicts oil and gas by using the seismic amplitude variation with offset, and it has become a trend in researches of geophysical inversion because of its full use of seismic gathers. According to Zoeppritz equation, we can get all remaining parameters from any three known parameters. Therefore, this paper chooses simultaneous inversion of P-impedance, S-impedance and density.Several researches on simultaneous inversion are conducted in this paper, analyzing core issues and inversion algorithms, and a complete process of pre-stack simultaneous inversion is established. The main work and achievements are listed as followed.(1) A precise AVO forward modeling is established in this thesis according to the basic theories of AVO and Zoeppritz equation as well as its approximate expressions.(2) In this paper, the mathematic model of simultaneous inversion is proposed according to convolution model, and the key technologies of inversion are analyzed, then a common process of simultaneous inversion is established.(3) Researches on simulated annealing algorithm are conducted in this paper, mainly introducing three key aspects, creating new model, accepting rule and time schedule. At the same time we elaborated the nature of simulated annealing and proved it reaches the global optimum.(4) Simulated annealing is applied in simultaneous inversion to overcome the shortages of linear algorithms for inversion problems, and we get good results through theory model test, approving the effectiveness of this method.(5) Simultaneous inversion software system is implemented in this paper and we achieved our method via C codes. The inversion results of P-impedance, S-impedance and density approved the application value of this system.