Method for estimating attenuation gradient of seismic waves based on variable mode decomposition

Abstract

The invention discloses a method for estimating the attenuation gradient of seismic waves based on variable mode decomposition. The method includes: calibrating a target layer by using logging, well logging and a synthetic seismogram; performing variable mode decomposition on seismic data on a trace by trace basis, and extracting the attenuation gradient of an intrinsic mode function in combination with the least squares algorithm, and making a weighted summation of the attenuation gradient of the intrinsic mode function and obtaining an attenuation gradient value of each earthquake trace; and determining the lithology of each target layer and hydrocarbons properties by using seismic attenuation gradient features. The method can be more effectively applied to attenuation gradient estimation of seismic signals with low signal to noise ratio and large frequency spectrum fluctuation. Therefore, the method can increase effectiveness of absorption attenuation gradient in indicating oil gas and is accurate in identifying lithology and hydrocarbons properties.

Description

technical field [0001] The invention relates to the technical field of petroleum geophysical exploration, in particular to a seismic wave attenuation gradient estimation method based on variable mode decomposition. Background technique [0002] As an inherent property of the medium, seismic attenuation is the energy loss that occurs during the propagation of seismic waves in the subsurface medium. In addition to wavefront divergence during seismic wave propagation in rocks, the incompletely elastic properties of rocks may also contribute to the attenuation of seismic energy. The total energy of the seismic wave is thus attenuated because the elastic energy of the seismic wave is irreversibly converted into thermal energy and then dissipated. There are many factors that affect the attenuation of seismic waves, but in a relatively stable stratum structure with little change in vertical and horizontal lithology, the attenuation of seismic waves is mainly caused by fluid proper...

AI Technical Summary

Problems solved by technology

Because conventional time-frequency analysis methods such as short-time Fourier transform are limited by the principle of uncertainty, the time-frequency resolution is low, and the applicability of the method is greatly limited due to some shortcomings of the respective methods, such as short-term Time Fourier transform is difficult to guarantee high enough resolution in time and frequency domain; the effectiveness of wavelet analysis depends on the choice of wavelet function; the wavelet basis function of S transform is fixed, which cannot meet the needs of actual data processing

In addition, using two-point slope or linear fitting method to obtain the attenuation gradient of energy and frequency is only suitable for seismic signals with high signal-to-noise ratio or seismic waves with smooth spectrum. The effect of large seismic waves becomes poor, especially when the noise energy in the high-frequency band is strong, and the absorption attenuation gradient cannot fully indicate oil and gas

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