Abstract: The information of petroliferous reservoir is hided in the level of differential waveform complexity between the resistivity and porosity log curves of reservoirs. The density of power spectral entropy, on the whole, is an exponential decline curve with frequency augmentation without reference to water flooded extent. Along with water flooded extent reducing gradually, the declining rate of power spectral is reducing and some frequency components are absorbed, the whole of which energy gradually falls. The curve changes gradually from slick to dentate form, and the power spectral entropy increases gradually. The signal power spectral entropy depends on the level of signal complexity and is independent of signal absolute value. It is indicated that the low resistivity oil layer and the high resistivity swept layer and water layer can be much better identified by the identification method of swept layer based on the power spectral entropy characteristic of log signal than by the conventional well log explanation theory.

Key words: flooded layer, spectral, entropy, resistivity, Tuha basin