High-resolution sequence stratigraphic division method based on EEMD (Ensemble Empirical Mode Decomposition)

Abstract

The invention relates to a high-resolution sequence stratigraphic division method based on EEMD (Ensemble Empirical Mode Decomposition), and belongs to the technical field of stratigraphic analysis. The high-resolution sequence stratigraphic division method based on EEMD comprises the following steps of: inputting logging data; performing EEMD empirical mode decomposition to obtain an IMF (Intrinsic mode function) component; adding equal-length unequal-amplitude Gaussian white noise to logging signals to be processed; performing EMD decomposition on composite signals; calculating the SNR (Signal-Noise Ratio) of the output IMF component, and removing a first IMF component with low SNR; carrying out the Hilbert transform on each IMF from the IMF2 component to obtain an HHT (Hilbert-Huang Transform) time frequency spectrum; deeply matching the geological horizon with the HHT time frequency spectrum obtained by each IMP, and calibrating the time frequency mutation point corresponding to the key geological horizon; and on the basis of the deeply matched HHT time frequency spectrum, carrying out the sequence division of all levels according to accuracy precision of a work area. The EEMD decomposition algorithm can well suppress the modal aliasing effect, the redundant error information caused by the algorithm is reduced, the recognition precision of a sequence interface is effectively improved, and the resolution of the sequence division is improved.

Description

technical field [0001] The invention belongs to the technical field of stratum analysis, and in particular relates to an EEMD-based high-resolution sequence stratigraphy division method. Background technique [0002] The division of different levels of sequence boundaries and the identification of the types of internal sedimentary cycles are important foundations for sequence stratigraphy analysis. The formation of sedimentary sequence cycles in sedimentary strata is the result of periodic changes in the sea (lake) plane, and is represented by the characteristics of sediment lithology, grain size, and stratum thickness, but in the process of sequence division by drilling lithology However, due to the actual lithology such as serious interbedded sand-mudstone layers and thick homogeneous lithology intervals, it is relatively difficult to divide the sequence by lithology, and it is difficult to manually distinguish the key sequence from the drilling lithology structure. inter...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that it is greatly affected by human experience. If a large set of strata with relatively consistent lithology is encountered, the transformation range of the logging curve is not obvious, and it is relatively difficult to identify the characteristics of the logging facies. Accurate division, let alone accurate judgment of the cyclicity of sequence stratigraphy

The disadvantage of this method is that, limited by the algorithm of wavelet transform itself, the frequency domain obtained by wavelet transform is limited by the distribution of wavelet windows, and often contains other frequency domain data, so the obtained time spectrum cannot be obtained in terms of frequency domain focusing. Accurate logging curve frequency, when the frequency spectrum is relatively too rough, directly affects the recognition accuracy of the sequence interface

The disadvantage of this method is that there will be obvious mode aliasing phenomenon when EMD is decomposed to obtain each IMF component. , there will be a phenomenon that the signal extends until it reaches a steady state at the sudden change of the signal in this frequency band, and the obtained HHT time spectrum appears in the time domain of the adjacent part after the single frequency signal is interrupted, which is not an effective signal time spectrum, thereby reducing The spectral resolution of HHT, and the sudden change of signal frequency often represents the interface of lithological mutation, so the frequency spectrum obtained by HHT has a large interference effect on the division of sequence stratigraphy, and the obtained results are not accurate.

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