Study On Methodology Of Seismic Anisotropy Inversion For Carbonate Fractured Reservoirs

With the deepening of the exploration and development of oil and gas,the exploration degree is becoming more and more difficult.Many oil companies all over the world have shifted the focus of exploration from conventional reservoirs to special oil and gas reservoirs such as carbonate fracture reservoirs.Carbonate fracture reservoirs are difficult to predict and the distribution of fractures is uneven.Therefore,it is especially important to find a geophysical inversion method to predict carbonate fracture reservoirs effectively.Based on the study of the geological characteristics of carbonate fracture reservoirs,the high-angle cracks,which are widely developed in carbonate fracture reservoirs.are equivalent to horizontal transverse isotropic with horizontal symmetry axes.The rock-physical model is used as a bridge to establish the relationship between the seismic response characteristics of the carbonate fracture reservoir and the geophysical elastic parameters.The inversion can be used to obtain the sensitive parameters indicating the carbonate fracture reservoir.It provides a strong and basic provement for the exploration and development of carbonate rock fracture reservoirs.By establishing an azimuthal anisotropic petrophysical model suitable for carbonate fracture reservoirs,combined with some conventional logging interpretation results as basic information for modeling,including mineral content,porosity,water saturation,etc.,the velocities and anisotropy parameters of the fracture reservoir can be estimated.We find the sensitive elastic parameters of the carbonate fracture reservoir,which lays a foundation for subsequent inversion and three-dimensional prediction;According to the law of reflection and transmission of the first waves in anisotropic media,based on the approximate formula of reflection coefficient,the approximate formula of anisotropic reflection coefficient including the sensitive parameters of carbonate rocks fractured reservoirs is derived.Then explore AVAZ inversion method of fracture reservoir.The azimuthal anisotropic elastic impedance formula is derived.Through the model test,it is proved that the inversion method has strong anti-noise performance.The inversion method is applied to the actual carbonate rock area,and the inversion results are in good agreement with the logging interpretation results.