Self-adapting wave form retrieval method through utilization of zero offset vertical seismic profile (VSP) data to estimate speed and Q value

Abstract

The invention discloses a self-adapting wave form retrieval method through utilization of zero offset vertical seismic profile (VSP) data to estimate speed and Q value. The method includes a first step of selecting undisturbed a segment of a first-motion wave in a self-adapting mode to the maximum extent according to the signal to noise ratio of the actual VSP data and the degree of a direct wave disturbed by an upward traveling wave, and fully utilizing effective information to construct an objective function, a second step of improving the sensitiveness of the objective function to changes of the Q value through proper construction of a data weighting matrix according to the feature that the Q value is more difficult to estimate than other parameters; a third step of adopting a recently developmental self-adapting multiplication regularization method to improve the ill-conditional problem of nonlinear inversion, and limiting the value range of the unknown parameters through nonlinear transformation, and a fourth step of inferring analytical expressions of elements of a jacobian matrix so as to decrease the calculated amount of inverse problems. Compared with a spectrum ratio method and a wavelet envelope peak value instantaneous frequency method, the method is relatively smaller in influence of the upward traveling wave, stronger in anti-noise performance, and higher in accuracy of inverse parameters.

Description

technical field [0001] The invention belongs to the field of geophysical exploration, and relates to an inversion method for physical property parameters of an earth model, in particular to a method for inverting medium velocity and quality factor Q by using zero-offset VSP seismic data based on the Gauss-Newton method. Background technique [0002] Seismic waves will gradually attenuate when propagating in the formation, and the attenuation factors include geometric diffusion, transmission / reflection loss, incomplete elasticity of the medium, and so on. The attenuation caused by the incomplete elasticity of the medium is an inherent characteristic of the medium, and this characteristic is often described by the quality factor Q. The attenuation caused by incomplete elasticity will affect the amplitude and phase of the seismic wave: if the Q value is known, the inverse Q filter can be used to enhance the high frequency components of the seismic signal, thereby improving the ...

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Problems solved by technology

Scholars at home and abroad have carried out a lot of research work in this regard, such as: Stewart [8] It is proposed to simultaneously use the full waveforms of four adjacent records to invert the velocity, attenuation factor, up-going wave and down-going wave in the frequency domain; Amundsen and Mittet [9] The phase velocity and quality factor Q are inverted in the frequency domain only by using the first arrival downgoing wave and the primary reflection wave. This method takes into account the variation of the reflection / transmission coefficient with frequency, but requires that the interface position and the medium density are known, which in some Difficult to satisfy in practical problems

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