Conjugate gradient normalized lsrtm method, system, storage medium and application

Abstract

The invention relates to a conjugate gradient normalized LSRTM method, system, storage medium and application, and belongs to the technical field of geophysical exploration. The method uses the conventional reverse time migration result as the input of the least squares inversion, and performs Born approximation on it. Forward modeling, the gradient calculation formula in the iterative algorithm is improved, the convergence speed of the algorithm is improved, the source normalized conjugation is used to calculate the update step size, and the migration profile that satisfies the convergence condition is continuously iteratively output. The imaging method can not only weaken the influence of the seismic source effect, reduce the low-frequency interference of the migration section, but also improve the deep illumination energy and imaging accuracy. Through improvement, the convergence speed of the algorithm is greatly improved compared with the conventional least squares reverse time migration algorithm, thus saving a lot of computing resources and cost. The invention provides high-efficiency and high-precision migration imaging services for the next step of seismic exploration interpretation work.

Description

technical field [0001] The invention belongs to the technical field of geophysical exploration, and in particular relates to a conjugate gradient normalized LSRTM method, system, storage medium and application. Background technique [0002] With the deepening of oil and gas exploration, exploration targets have gradually evolved from simple structures to complex structures, and migration imaging methods have also gradually developed, from the initial Kirchhoff migration and Beam migration based on ray theory to the one-way wave and dual-way migration. The reverse time migration of Cheng wave, and then the least squares reverse time migration based on the inversion theory. Among the current migration imaging methods for complex structures, the reverse time migration method based on the two-way wave equation is widely used. Compared with other conventional migration methods, it has the following advantages. First, it is not limited by the dip angle, and can image a variety of...

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Problems solved by technology

However, the main problem of reverse time migration is that the migration operator is only the conjugate transpose of the forward operator, not its inverse. In addition, due to the limited acquisition aperture, complex subsurface model and limited seismic wave bandwidth, the reverse time migration Migration can only provide vague structural information, and cannot perform fine imaging of complex oil and gas reservoirs

However, the conventional least-squares reverse-time migration generally uses the cross-correlation conjugate gradient method for iteration. This iteration method is greatly affected by the source effect, and there is low-frequency interference in the migration imaging results. The deep imaging amplitude is weak and it is difficult to identify Deep effective energy information

At the same time, its slow convergence speed will lead to a very large amount of calculation and storage requirements, which will greatly increase the cost of processing data

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