Pre-stack time migration method based on split-step Fourier algorithm

Abstract

The invention provides a Pre-stack time migration method based on a split-step Fourier algorithm. The method comprises the steps of inputting pre-processed seismic data; picking up the root mean square speed in an interactive mode; calculating the ray propagation time from an imaging point to a focus point; converting seismic data of a time-space domain into frequency-wave number; acquiring a continuation value of a background wave field; transforming the continued wave field into the frequency-space domain through Fourier transform, and performing a time shift operation through a split-step Fourier time shift operator of the time domain so as to realize continuation for a disturbance wave field; and performing phase shift on a frequency-space domain seismic wave field and carrying out integration on the effective frequency band by using a excitation time imaging condition so as to acquire a seismic imaging result of a shot record. The pre-stack time migration method based on the split-step Fourier algorithm can carry out migration by applying the root mean square speed, and improves the adaptive capacity for speed vertical and longitudinal variations and the amplitude preserving capacity for migration imaging of pre-stack time migration under the condition of not increasing the speed modeling difficulty.

Description

technical field [0001] The invention relates to the field of migration imaging in seismic data processing, in particular to a pre-stack time migration method based on a sub-step Fourier algorithm. Background technique [0002] Seismic migration is an inversion operation that rearranges seismic information in order to return the energy of seismic waves to its real position in space and obtain the real structure of the underground. Wave equation prestack migration imaging is mainly divided into two types: prestack time migration imaging and prestack depth migration imaging. Prestack depth migration is highly adaptable to lateral changes in subsurface velocity and can provide high-quality imaging results in the depth domain. However, it requires high accuracy of the velocity model and requires a large amount of calculation. Therefore, it is a high-input and high-return solution. Pre-stack time migration imaging has high computational efficiency, and at the same time, it has lo...

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Problems solved by technology

This method has a high imaging angle, but the amount of calculation is large. The wave field is calculated by linear interpolation, which cannot adapt to large changes in lateral velocity.

[0008] Sergey fomel (2013) proposed a method to solve the wave equation from the Cartesian coordinate system to the imaging ray coordinate system. This method avoids the approximate solution of the Green's function calculation in the conventional time migration and improves the time migration. Calculation accuracy, but its adaptability to lateral changes in speed is poor

[0009] Due to the good numerical characteristics of the wave field method, the prestack time migration of the wave field method has important practical value. Many research works try to use the calculation characteristics of the wave field method, but they are limited by the reference to the root mean square velocity and adapting to velocity changes. Two problems, it is difficult to meet the practical requirements

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