Research On Method Of Stress Calculation In Transversely Isotropic Formation Using Logging Data

In recent years,gradually we regard the exploration and development of unconventional resource as an important goal,which needs to be fracturing and influenced by formation pressure and other factors.So it is very important for the formation pressure evaluation.During drilling,formation always has obvious inhomogeneity and anisotropy,so the study of anisotropy has been paid more and more attention.Sandstone,shale has strong anisotropy,particularly the most typical transversely isotropy.So the analysis of anisotropy in transversely isotropic formation is particularly important.However,the isotropic model we used before does not apply to anisotropic formations,therefore we need to establish a transversely isotropic stress calculation model.Logging data is the only way to obtain a continuous pressure parameter in a borehole profile.So this paper studies the sound field characteristics in isotropic and anisotropic formation of fluid-filled borehole with forward simulation method.and supply a method for extracting acoustic parameters in transversely isotropic formation.On this basis,we research the method for inversing of formation anisotropy parameters,we establish a transversely isotropic stress calculation model.This paper not only simulates the wave field and dispersion characteristics in the model of Isotropy and transversely isotropy,but also simulates the influence on wave field response brought by logging tools.The simulation results show that the low-frequency Stoneley wave is sensitive to the wave that spreads along the horizontal direction,and the logging tools changes the dispersive characteristics of Stoneley wave significantly.Therefore,when we invert to get the formation anisotropy using acoustic logging data,we must consider the elastic parameters of logging tools.We apply spectrum weighted average method to obtain the shear wave velocity which spreads along the horizontal direction from sonic logging data,then we calculate the elastic parameters such as Young's modulus,Poisson's ratio and so on based on transversely isotropic model.Comparing to the results based on isotropic model,the results based on transversely isotropic model are different significantly.Anisotropic elastic parameters obtained by acoustic logging data,combined with other logging data such as density logging,gamma logging data establish a transversely isotropic stress calculation model,under which the results are different to the results under the isotropic stress calculation model significantly.The parameters we get such as the size and orientation of the formation pressure and the fracture pressure based on transversely isotropic model have a very important significance to improve the completion and fracturing design.