Characteristics Of Multi-wave Seismic AVA Response Caused By Hydrocarbon And Lithology Changes

AVO (or AVA) is a Seismic exploration technique which makes use of the characteristic of amplitude variation with offset to analyze and identify Lithology and reservoir. According to the seismic wave theory of reflection and transmission, amplitude variation with angle of incidence related with the seismic parameters of the medium on both sides of the interface, which contains two meanings: first, with different lithological parameters, the characteristics of amplitude vary with the angle of incidence. Second, using AVA forward model to analyze the known oil, gas, water and lithology AVA feature helps to identify lithology, oil and gas from seismic records, and to describe reservoir qualitativly. Amplitude coefficient itself implies lithologic parameters, densityρ, longitudinal wave velocityαand S-wave velocityβof rocks can be inversed directly in use of AVA characteristics, so we can describe reservoir quantitatively.The purpose of this thesis is modeling the AVA characteristics of different oil, gas and water saturation on single interface and thin-layer, and analyzing the characteristics of multi-wave seismic AVA response caused by hydrocarbon and lithology changes in typical isotropic reservoir, in order to provide the study of joint AVA inversion of multi-wave a baisc. At the same time, analyzing the AVA characteristics of multi-wave exhaustivly, so as to provide a theoretical basis for the identification of thin-layer. Meanwhile, making a comparison between the Single interface and thin-layer AVA characteristics, and proposing a method that identifies thin layer with the help of AVA characteristics.At the same time, in this thesis, we have given a detailed elaboration about how to get the AVA curve of single interface and thin-layer. We should get the reflection coefficient value at the the tuned frequency, only in this way can we receive the AVA curve which is closer to the forward calculation.