Analysis Of Lithology And Reservoir Characteristics Based On Spectrum Characteristics Of Logging Data

All along,the reservoir lithology and reservoir physical properties are the key and difficult issues of geological interpretation of logging.Due to the complexity of underground lithology and reservoir conditions,the drilling lithology engineering volume and the cost of manpower and material resources are relatively large.Therefore,various methods of reservoir lithology identification analysis and reservoir physical property parameter prediction are widely used.For example,the rapid development of well logging technology and the use of computers have greatly improved lithology identification.Spectral analysis is a scientific lithological analysis method.It is based on geophysical well logging and uses related lithological data as primary data to further analyze the physical characteristics of lithology through a computer.The spectral analysis of lithology has been studied for a long time.Spectrograms and frequency domain parameters accurately show the types of underground lithology and lithology-related physical characteristics,which provide new ideas and methods for the effective use of logging information for geological interpretation.Based on the spectral decomposition technique,this paper introduces the basic principles and implementation methods of time-frequency analysis methods such as fast Fourier transform and continuous wavelet transform in detail,and compares the advantages and disadvantages of different methods.On this basis,another intuitive spectrum analysis method is introduced,namely,a one-dimensional wavelet transform and fast Fourier transform(Continuous wavelet transform using FFT algorithm,hereinafter referred to as CWTFT).First,a large number of numerical simulation experiments are carried out by using synthetic simulation signals and collected musical instrument vocal signals,such as a large number of artificial signals and signal data of piano and guitar musical instruments to check the reliability,stability and abnormalities of the CWTFT method,and detailed It explains some abnormal conditions in the spectrum chart,such as the "common frequency" and"resonance" phenomena,and provides an effective tool and means for the study of lithology and reservoir characteristics in the time-frequency domain.Based on the actual logging data of several wells in the Upper Paleozoic in the Dongpu Sag,the logging curves with good continuity and wide lithology distribution were selected.In this paper,a total of 16 wells in the Dongpu Depression were selected for the sandstone section and the natural gamma curve(GR)of carbonate rocks.The carbonate rocks mainly include limestone and dolomite as the sample test data for spectrum analysis.The CWTFT method was used to analyze the spectral characteristics of GR curves of different well sections or the same lithology in the same well section.The results showed that when the frequency values were 0.2Hz,0.3Hz,0.5Hz,0.7Hz,and 1.0Hz,the Benxi Formation,Taiyuan Formation,Shanxi The frequency spectrum of the sandstone sections of the group,the lower Shihezi Formation,the upper Shihezi Formation,and the Shiqianfeng Formation all have obvious responses,and the intensity is higher.At frequency values of 0.3Hz,0.6Hz,and 1.0Hz,the frequency spectrum of carbonate rocks(dolomite,limestone)in the Benxi Formation,Taiyuan Formation,Shanxi Formation,Xiashihezi Formation,Shangshihezi Formation,and Shiqianfeng Formation are obvious.Response,and the display intensity is higher.Using this method,the detrital rocks in the Wengu 3 and Qinggu 1 sections,and the carbonate rocks in the Kai 3 and Magu 6 sections were effectively identified.Subsequently,the related functions of "sound" in Matlab software were used to "sound"the logging curve,and an attempt was made to infer the lithology characteristics indirectly by using the difference in sounds.Finally,after continuous wavelet transform of GR and AC of the Dongpu Sag Reservoir Logging Curve,it is found that there are good oil and gas shows that the GR value of the formation is generally low to medium,the shape of the curve includes a toothed box shape,and the chromatogram appears The multi-scale spectrum superposition phenomenon,the scale value is mainly 51,94 and 158;At the same time,the AC value is low,and the multi-scale spectrum superposition phenomenon also appears in the chromatogram,the scale value is mainly 40,90 and 131,based on this,The identification and prediction of the Qinggu 3 well suspected oil and gas layer positions 3510?3522m,3592?3607m and 3673?3687m.