Research And Application Of Time-frequency Analysis Of Seismic Data Based On Empirical Mode Decomposition(EMD)

As the difficulty of seismic exploration and development increases,the difficulty of seismic data processing and interpretation also increases.A single method is often difficult to achieve a fine characterization of geological bodies.In order to use seismic data reasonably,and obtain important seismic exploration information from seismic data,and then extract key reservoir attributes,find a more efficient method for reservoir characterization.In this paper,from the research of conventional time-frequency processing methods,we focus on a series of methods based on empirical mode decomposition(EMD),expand the new method based on EMD and effectively apply it to the reservoir,providing for the identification and characterization of oil and gas new basis.(1)The core algorithm of this paper is an improved complete empirical mode decomposition method(ICEEMD).The new method of oil and gas detection based on traditional ICEEMD is expanded,which provides a new basis for reservoir characterization and hydrocarbon detection.This article starts from empirical mode decomposition(EMD)and compares modal decomposition methods such as ensemble empirical mode decomposition(EEMD),complete set empirical mode decomposition(CEEMD),and improved complete set empirical mode decomposition(ICEEMD).Among them,EEMD,CEEMD and ICEEMD are all developed from empirical mode decomposition(EMD).By comparing these four empirical modal decomposition methods,we can see that the improved complete empirical modal decomposition method(ICEEMD)can effectively solve the problems of modal aliasing and residual noise in signal decomposition.Therefore,a joint time-frequency analysis method based on ICEEMD is proposed in this paper to extract the instantaneous attributes and attenuation gradient attributes,respectively,so as to achieve the purpose of reservoir prediction and hydrocarbon detection.(2)A joint spectral decomposition algorithm based on ICEEMD and TK energy operator is proposed.The traditional Hilbert-Huang transform(HHT)transform is a time-frequency analysis method for nonlinear and non-stationary signal processing.However,this method has problems such as endpoint effects and modal aliasing,resulting in low signal recognition accuracy.Although Improved Complete Ensemble Empirical Mode Docomposition(ICEEMD)can solve the problem of modal aliasing well,the instantaneous amplitude and instantaneous frequency extracted in combination with Hilbert transform still have severe endpoint effects.It is not well applied to reservoir prediction based on actual data.TK energy separation algorithm is a non-linear algorithm that uses the difference operation to calculate the instantaneous properties.It has a higher time resolution than the Hilbert transform.Due to the algorithm itself,TK energy can only be applied to single-component signals and cannot be directly applied to complex seismic data.Therefore,this paper combines the advantages of the improved complete empirical modal decomposition method and the TK energy separation algorithm to extract the instantaneous amplitude and instantaneous frequency of the actual seismic record and perform reservoir prediction in a work area in the South China Sea.The prediction results are in good agreement with the log data.The high recognition accuracy proves that the method can accurately reflect the reservoir characteristics.(3)A method based on ICEEMD and generalized S transform to extract attenuation gradient is proposed.The improved complete empirical mode decomposition(ICEEMD)is a new extension of the complete empirical mode decomposition(CEEMD)algorithm,which effectively solves the problems of residual noise and modal aliasing generated by CEEMD in signal decomposition.In addition,ICEEMD can better detect weak signals in gas-bearing layers.The generalized S transform has high time-frequency focus in seismic signals,and can clearly extract the characteristic information of seismic signals.Based on the above advantages,this paper proposes a method of combining ICEEMD and generalized S transform to analyze seismic attributes in a work area in the South China Sea to detect the oil and gas situation in the area.The results for a work area in the South China Sea show that the method proposed in this paper can clearly characterize the strong amplitude anomalies of the reservoir,and the results of oil and gas interpretation given are consistent with known gas test results.