A Study On P-Wave Velocity Analysis Method In Azimuthally Anisotropic Media

Conventional method of velocity analysis is based on the assumption of isotropy, and hyperbolic moveout processing on short spreads is sufficient for this case. But numerous researches during the past decade have showed the presence of seismic anisotropy in different geological settings and on various scales. There is a growing understanding that the influence of anisotropy leads to the deviations of moveout curve from a hyperbola, and nonhyperbolic moveout analysis is important to recover anisotropic velocity fields from surface reflection data.In this paper, by analyzing various influential factors on velocity analysis accuracy synthetically,several optimize measures are listed. Secondly, fraction expansion time-distance equation in anisotropic media is derived, which has a term ensuring convergence at large offsets, and according to the equivalence of kinematical characters between VTI and within symmetry planes of HTI and OA medium, extend the derived nonhyperbolic approximation to azimuthally anisotropic media,then establish the azimuthal relation of moveout. Next, a study of P-wave nonhyperbolic moveout velocity analysis in azimuthally anisotropic media is performed. Model test is proceeded by interactive mode, and the inversion of movout velocity and anisotropic parameters is carried out in actual data,the results of which demonstrates the accuracy and practicability of this method.