Seismic Wave-field Modeling And Prestack Depth Migration Based On One-way Wave Operator

The seismic data processing is mainly based on analyzing and using primary reflection, the multiple reflections and other wave-fields are interpreted as noises at the present time.The one-way wave equation algorithms enable to simulate the primary reflection from construction of complex media.Compare with the full wave equation, the one-way wave equation has many advantages:high calculating fficiency, useful in velocity modeling for its mathching of regular migration algorithms, flexibly controlling wave-field that is simulated.It can not only simulate various kinds wavefields at the same time,but also separately simulate wavefield that is required.Firstly, the paper derives one-way acoustic wave equation in inhomogeneous medium by approximating full acoustic equation, and gets completely decoupled one-way wave equation by making reasonable assumptions to real medium.Secondly, frequently-used principles that are based on one-way wave equation are introduced, the split-step Fourier operator, pseudo screen operator, high order generalized screen propagator, stable extended local Born Fourier operator, pade screen operator and its reduced form are deduced.A globally optimized Fourier finite-difference method that uses a rational approximation of the square-root operator in the one-way wave equation is developed, the two coefficients in the rational approximation are determined by using an optimization scheme that maximizes the maximum dip angle for a given model.Thirdly, the principles of using one-way wave equation to simulate nonzero offset seismic wavefield are described.The internal relation of several types of one-way wave operators has been analyzed by a separable approximation for the one-way wave operator.The main points of imaging complex media are wave-field extrapolation operator with strong lateral velocity contrasts and accurate imaging conditions.The adaptability of one-way wave operators to deal with strong lateral velocity variations is analyzed.Correlated imaging condition is used to calculate imaging value.Model test results demonstrate that the Pade screen operator and Fourier finite-difference operator can well adapt the strong lateral velocity contrasts.The validity of the proposed methods is verified by modeling and imaging to data model.