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

Abstract

The invention discloses a method for analyzing the frequency domain anomaly of the underground medium in the work area. The method for analyzing the frequency domain anomaly of the underground medium in the work area is characterized in that it includes the following steps: through the petrophysical analysis of the logging data, the sandstone of the underground medium in the work area is distinguished Stratum and mudstone formation; through the time-frequency analysis algorithm, the frequency information data of the seismic data in the sandstone formation and mudstone formation of the work area are obtained; through the seismic wave attenuation feature extraction technology, the attenuation feature extraction is performed on the frequency information data, and the seismic data in the sandstone formation is obtained. and the frequency attenuation characteristic parameters of the mudstone formation; use the least square method to perform linear fitting or polynomial fitting on the attenuation characteristic parameters to obtain the attenuation trend line of the sandstone formation and the attenuation trend line of the mudstone formation; the attenuation trend line of the sandstone formation is the main , with the attenuation trend line of the mudstone formation as an attachment, the difference of the attenuation trend of the seismic data in the sandstone formation and the mudstone formation is analyzed.

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

[0060] (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

[0061] (2) Disadvantages of wavelet transform: wavelet transform is a multi-scale method that analyzes different frequencies with different scales. 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

[0062] (3) Disadvantages of S-transform: S-transform solves the phase localization problem of wavelet transform, but it actually implies that there is 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) and the zero-crossing place have a large difference in amplitude

[0063] 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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