Method for predicting fracture azimuth angle based on transverse wave polarization analysis

Abstract

The invention discloses a method for predicting a fracture azimuth angle based on transverse wave polarization analysis. The method comprises the following steps of: 1, assuming that a single group of vertical fractures are distributed in a stratum, and acquiring converted waves of seismic waves; 2, determining a time window according to a wavefront moment and a wave tail moment; step 3, performing scanning iteration on the seismic signals in the time window from two ends to the middle, and ending iteration when the transverse wave polarization vector and the fast and slow wave time difference after each iteration and the result of the last iteration are smaller than a set value; 4, according to the crack direction vector obtained in the step 3, obtaining an included angle between the crack and the direction of a connecting line between the seismic source and the receiver; the azimuth angle is iteratively calculated based on polarization data in a fast and slow shear wave time window and a fast and slow shear wave cross-polarization hypothesis; the number of iterations is smaller, and the calculation speed is higher; the crack azimuth angle is calculated through iteration of multiple sample points, the influence of noise is reduced through multiple times of iteration, and the calculation precision is higher.

Description

technical field [0001] The invention relates to the technical field of seismic exploration, in particular to a method for predicting fracture azimuth angles based on shear wave polarization analysis. Background technique [0002] Accurate prediction of fracture parameters is of great significance to the exploration and development of fractured reservoirs, and it is also a difficult point in the process of exploration and development of fractured reservoirs. Existing fracture prediction methods based on multi-wave seismic data mainly use shear wave birefringence to predict fracture parameters. Crampin confirmed for the first time the existence of shear wave splitting in anisotropic media, and the polarization direction of fast shear waves is consistent with the direction of fractures, and studied the characteristics of shear wave polarization in VSP data. There are a series of methods for fracture prediction in the time domain based on the phenomenon of shear wave splitting,...

AI Technical Summary

Problems solved by technology

When shear wave splitting occurs, although the fast and slow waves are orthogonally polarized to each other, when the fast and slow waves are not separated in the time domain, but are coupled with each other, a straight line cannot be fitted to indicate the fracture direction

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