Petroleum Exploration and Development (Dec 2021)
A microscopic ancient river channel identification method based on maximum entropy principle and Wigner-Ville Distribution and its application
Abstract
In view of the problem of fine characterization of narrow and thin channels, the maximum entropy criterion is used to enhance the focusing characteristics of Wigner-Ville Distribution. On the basis of effectively improving the time-frequency resolution of seismic signal, a new method of microscopic ancient river channel identification is established. Based on the principle of the equivalence between the maximum entropy power spectrum and the AR model power spectrum, the prediction error and the autoregression coefficient of AR model are obtained using the Burg algorithm and Levinson-Durbin recurrence rule. Under the condition of the first derivative of autocorrelation function being 0, the Wigner-Ville Distribution of seismic signal is calculated, and the Wigner-Ville Distribution time-frequency power spectrum (MEWVD) is obtained under the maximum entropy criterion of the microscopic ancient river channel. Through analysis of emulational seismic signal and forward numerical simulation signal of narrow thin model, it is found that MEWVD can effectively avoid the interference of cross term of Wigner-Ville Distribution, and obtain more accurate spectral characteristics than STFT and CWT signal analysis methods. It is also proved that the narrow and thin river channels of different scales can be identified effectively by MEWVD of different frequencies. The method is applied to the third member of Jurassic Shaximiao Formation (J2s33-2) gas reservoir of the Zhongjiang gas field in Sichuan Basin. The spatial information of width and direction of narrow and thin river channels with width less than 500 m and sandstone thickness less than 35 m is accurately identified, providing bases for well deployment and horizontal well fracturing section selection.
