![frequency spectrum beatunes frequency spectrum beatunes](https://www.allaboutcircuits.com/uploads/articles/RFT_ch4_pg3_FMm1spectrum.jpg)
Thus by multiplying a given signal function with a reference sine wave, the DC component of the product is proportional to the in-phase signal component at the reference frequency. The product of a sine and cosine wave of equal frequency contains no DC component. The product of two sine waves of equal frequency and phase difference not 90° contains a DC component. That is to say, the weight of logging is 0.61.įrequency Spectrum Analysis Fundamentals (see Eq. By virtue of the stratigraphic correlation diagram and the constraint and calibration of well-tie inversion, the search radius is determined to be 0.61. During the selection of search radius, the weight of logging in the inversion should not be blindly increased for the purpose of vertical resolution instead, the weight should be decreased to guarantee the lateral resolution while the single-stage fan can be identified. If multiple wells are used in the seismic model inversion, the vertical resolution of the inversion can be improved effectively while the lateral resolution is decreased. The larger the search radius is, the larger the weight of seismic in inversion is otherwise, the weight of logging in inversion is larger. The optimal well extrapolation factor is five. Therefore, well-tie sedimentary section facies, seismic facies, and well-tie model inversion sections are taken as the constraints to determine the well extrapolation factor. A sublacustrine fan is composed of sedimentary rocks deposited in a high-energy environment and its lithofacies change is fast, so the well point information cannot be extrapolated too far. The higher the well extrapolation factor is, the faster the change is and the shorter the extension distance is. The well extrapolation factor mainly reflects the lateral extension distance and variation gradient of well point information. After multiple tests, it is determined that the fractal index is 0.42. When the model inversion modeling parameters are selected, the fractal modeling method can reflect the change characteristics of sublacustrine fans more accurately because of their characteristics of large thickness change and fast lithofacies change.
![frequency spectrum beatunes frequency spectrum beatunes](https://www.gps.gov/spectrum/allocations.jpg)
Then, the logging constrained model inversion is adopted to realize high-resolution prediction. Therefore, the high-frequency extension band is supplemented by means of time-variable frequency division deconvolution, so as to increase the resolution of seismic data. The amplitude decline gradient of dominant frequency is smaller in the direction of high frequency, and the seismic data above 42 Hz have certain energy, with a signal-to-noise ratio (SNR) of higher than one. Frequency spectrum analysis shows that the dominant frequency of the seismic data of the study area is about 20 Hz and the effective frequency band is 6–42 Hz.
![frequency spectrum beatunes frequency spectrum beatunes](http://s3.amazonaws.com/pbblogassets/uploads/2014/02/frequencyspectrum.jpg)
In the middle-late stage of exploration, there are more wells and the constraint of wells on seismic prediction is stronger, so that high-resolution seismic inversion is often used. Xiugang Pu, in Re-exploration Programs for Petroleum-Rich Sags in Rift Basins, 2018 Prediction in the middle-late stage of exploration