Method for anomaly analysis of frequency domain of underground medium of work area

Abstract

The invention discloses a method for anomaly analysis of the frequency domain of an underground medium of a work area. The method is characterized by comprising the steps of distinguishing a sandstone formation from a mudstone formation of the underground medium of the work area through rock physics analysis of logging data, working out frequency information data of seismic data of the work area in the sandstone formation and frequency information data of the seismic data of the work area in the mudstone formation according to the time-frequency analysis algorithm, carrying out attenuation characteristic extraction on the frequency information data according to the seismic wave attenuation characteristic extraction technology to obtain frequency attenuation characteristic parameters of the seismic data in the sandstone formation and attenuation characteristic parameters of the seismic data in the mudstone formation, carrying out linear fitting or polynomial fitting on the attenuation characteristic parameters according to the least square method to obtain an attenuation trend line of the sandstone formation and an attenuation trend line of the mudstone formation, and analyzing the difference between the attenuation trend of the seismic data in the sandstone formation and the attenuation trend of the seismic data in the mudstone formation with the attenuation trend line of the sandstone formation as the main basis and the attenuation trend line of the mudstone formation as the auxiliary basis.

Description

technical field [0001] The invention relates to the technical field of offshore oilfield engineering, in particular to a method for analyzing anomalies in the frequency domain of underground media in a work area. Background technique [0002] As power energy, oil and natural gas control the development of the national economy and the lifeline of national strategy. The independent exploration and development of oil and natural gas is an important pillar for maintaining national stability and international competitiveness. Accurately predicting reservoirs and reservoir oil-gas properties is particularly important in oil and gas development. Since the last century, the technology of using geophysical exploration methods to find oil and gas reservoirs has been developed and applied. In this century, as simple structural oil and gas reservoirs have been basically explored, complex lithology fractured oil and gas reservoirs are the current oil and gas exploration. The main goal,...

AI Technical Summary

Problems solved by technology

[0055] (1) Disadvantages of short-time Fourier transform: Although STFT makes up for the lack of local analysis ability of conventional Fourier transform to a certain extent, it also has its own insurmountable defects, that is, when the window function is determined, the shape of the rectangular window It is determined, and the corresponding time resolution and frequency resolution are also determined, which cannot change with the change of signal frequency, and have no self-adaptive ability

Therefore, we must choose a reasonable time window length when performing short-time Fourier transform time-frequency analysis. If the time window length is too short, there will be high-frequency artifacts, and if the time window length is too long, there will be frequency overlap at different times, reaching Not for the purpose of time-frequency analysis

[0056] (2) Disadvantages of wavelet transform: Wavelet transform is a multi-scale method that analyzes different frequencies with different scales. It can give better time accuracy, and has good frequency accuracy in the low frequency area, while in the high frequency area The frequency resolution ability of the area is weak, and the wavelet transform has a fatal weakness. The wavelet transform is an absolute translation along the time direction, which implies that the modulation propagates along the envelope direction, which causes the phase information to be only partial and lose its physical meaning. incomprehensible

[0057] (3) Disadvantages of S-transform: S-transform solves the phase localization problem of wavelet transform, but it actually implies a window, so the frequency description is inaccurate where the frequency is discontinuous, and it is also difficult to accurately describe the amplitude value. (Valley value) has a large difference from the amplitude value at the zero crossing point

[0058] Disadvantages of frequency anomaly calculation: At present, the analysis of formation attenuation anomalies mainly uses the geodetic trend background, without considering the differences between different lithologies. Therefore, the calculated anomalies are strongly influenced by lithology, and there are also great differences in oil and gas detection. Uncertainty, how to evaluate attenuation anomalies by lithology is the key to oil and gas detection using frequency attenuation

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