Abstract：The selection of aperture angle is most direct and key factor for affecting the precision and efficiency of 3D seismic wavefield extrapolation.Using Rayleigh integration formula I in space-frequency domain,the paper deduced theoretically the precision of wavefield extrapolation for both single-pole and dipole sources,then deduced the analytic formula of errors.The analysis showed that the errors of amplitude mainly depend on aperture angled,the other parameters such as frequency /,velocity v and normal distance z only have limited influence on errors of phase.Numeric modeling by gritting the extrapolated reference plane and replacing integration with stack of wave function at discrete grit,the paper tested the correctness of the analytic formula.Finally,the paper presented the selected criterion of optimal aperture angle with hi-fi 3D wavefield extrapolation (precision of amplitude ^ 80%):the angle 6 is selected as great than 60° for single pole source and the angle d is selected as great than and equal to 55° for dipole source.This criterion can be used for theoretic study but it must do concrete analysis and synthetic balance when using it to solve the practical problems.
