Fractal analysis based on the continuous wavelet transform and lithofacies classification from well-logs data using the self-organizing map neural network

The main goal of this paper is to show that the fractal analysis based on the continuous wavelet transform is not able to improve lithofacies classification using the self-organizing map (SOM) neural network model from well-logs data. The proposed idea consists to inject many inputs in SOM neural network machines and to choose the best map. These inputs are: data set 1: the five raw well-logs data which are: the gamma ray, density, neutron porosity, photoelectric absorption coefficient and sonic well-log; data set 2: the estimated Hölder exponents using the continuous wavelet transform of the data set 1; data set 3: data set 1 and the three radioactive elements concentrations; data set 4: the estimated Hölder exponents of the data set 1 and the Hölder exponents of the radioactive elements concentrations; data set 5: the estimated Hölder exponents of the data set 1 and the three radioactive elements concentrations logs. Application of the proposed idea at two boreholes located in the Algerian Sahara shows that the Hölder exponents estimated with the continuous wavelet transform as an input of the SOM neural network are not able to give geological details. However, the raw well-logs as an input give more details and precision especially when they are enhanced with the natural gamma ray spectrometry dat

Nonlinearity, scaling and complexity in exploration geophysics

During last decades fractal analysis and in a given measure its multifractal generalization(s), have become very popular tools in exploration geophysics. In petrophysics fractal and multifractal analyses are used for reservoir characterization and in geomagnetism and gravity, they are used for causative sources characterization. In seismic data analysis, fractal analysis is being used for scaling deconvolution of the colored signal of reflectivity. The purpose of this special issue is to gather scientific researches related to this topic to show the utility of the fractal analysis in exploration geophysics. The topic of this issue is related to nonlinearity, scaling and complexity of earth system applied in different fields of exploration geophysics