Method Research Of Seismic Pre-Stack Depth Migration Based On One-Way Wave Operator

At present, the geological condition of seismic exploration is becoming more and more complex, and the requirement of imaging accuracy is becoming higher and higher. With the development of seismic exploration, especially for the underground medium that the lateral velocity variation is large, the pre-stack depth migration technique is developed, the pre-stack depth migration technology has a better imaging for the underground complex geological conditions. Not only for the lateral velocity variation larger medium, but also for the geological conditions that the reflective layer dip angle is bigger. Pre-stack depth migration technique has been widely used in complex area and deeper seismic exploration. The last section of seismic exploration has a great relationship with the seismic migration technology, and the migration technique has a direct impact on the final results of seismic exploration.Firstly, according to the theory of one-way wave equation decoupling, the paper completed the decoupling and one-way wave decomposition of the second order non homogeneous wave equation, getting the one-way wave equation which is more intuitive and efficient on the uplink and downlink wave direct extension. By the one-way wave equation, I deduced several offset continuation operator, and compared the relative error of the Split step Fourier operator and the Fourier finite difference operator and the Generalized screen operator of the first order and third-order operator, and analyzed the advantages and disadvantages of several operators. Then, we used the zero time and non-zero offset imaging condition to extract the imaging value. Finally, using the continuation operator, We programmed,the pre-stack seismic migration, and completed the migration in the shot domain for the graben model, the undulating ground model and the SEG salt model.Though the analysis of the velocity model, boundary conditions and the continuation step three key factors to offset the impact, the results show that the importance of velocity model and boundary conditions, and appropriate extension step length influence on the effect of imaging and computational efficiency; And we analyzed and compared the imaging accuracy and efficiency of several operators, getting that the Generalized screen operator of the first order has higher efficiency in the lateral velocity variation small medium taking into account the calculation speed and imaging precision. But in the larger horizontal velocity variation medium we choose Fourier finite difference operator better.