Earthquake stratum thickness variation analysis method

Abstract

The invention discloses an earthquake stratum thickness variation analysis method in which a high-resolution instantaneous frequency decomposed on the basis of an empirical mode is used to analyze stratum thickness variation. Firstly, an earthquake signal is subjected to an empirical mode decomposing process to obtain a multilevel intrinsic mode function; then, the instantaneous frequency of the intrinsic mode function is calculated; and according to the variation of the instantaneous frequency, the stratum thickness variation is analyzed. According to the earthquake stratum thickness variation analysis method, a triple B spline is adopted as an interpolating function in the empirical mode decomposing process; the instantaneous frequency is calculated by using an instantaneous frequency calculation method with a damping factor on the basis of continuous wavelet transform; the obtained intrinsic mode function and instantaneous frequency profile have good lateral continuity and few false appearances, accord with the reality and also have good noise immunity. The earthquake stratum thickness variation analysis method is favorable for improvement of the reliability and the effectiveness of the earthquake stratum thickness variation analysis, is suitable for processing and explaining practical earthquake data, provides a powerful basis for predicting a reservoir stratum, and improves the precision of oil-gas field exploration and development.

Description

Technical field: [0001] The invention relates to a seismic processing and interpretation method in seismic exploration, in particular to a high-resolution seismic stratum thickness variation analysis method based on empirical mode decomposition and instantaneous frequency. Background technique: [0002] The instantaneous attributes currently used in the analysis of seismic formation thickness variation mainly refer to the instantaneous attributes based on the conventional Hilbert transform, including instantaneous amplitude, instantaneous phase, and instantaneous frequency. Among them, the instantaneous frequency can be used for analysis of formation thickness variation and anomaly analysis. Seismic events are usually synthesized from seismic waves reflected by a set of reflecting interfaces in the subsurface. When the thickness and lithology of this group of reflection structures change gradually, the instantaneous frequency of the corresponding synthetic seismic wave also...

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Problems solved by technology

[0011] (2) The instantaneous frequency resolution based on the conventional Hilbert transform is low, it is not sensitive to the thickness change of the thin layer, and is greatly affected by noise, so it is difficult to judge the thickness change of the thin interlayer structure

[0015] (1) For single-trace seismic records, only the longitudinal thickness change of the formation can be analyzed;

[0016] (2) In the process of empirical model decomposition, the use of cubic splines as interpolation functions has overshoot and undershoot problems, and the fitted local maximum and local minimum envelopes are greatly affected by data sampling point fluctuations or small disturbances , the local maximum and minimum envelopes with large deviations may be obtained, which makes the empirical model decomposition results of adjacent channels change greatly, which leads to poor lateral continuity of the profile, and it is impossible to analyze the formation from the entire profile. Lateral thickness variation, it is difficult to be widely used in actual seismic signal processing

[0017] (3) In the process of empirical mode decomposition, the basic conditions for defining the intrinsic mode function are used to judge whether the filtered signal is an intrinsic mode function, resulting in low calculation efficiency and a large amount of calculation; the intrinsic mode function satisfies the basic conditions Yes:

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