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Analysis of Well log Data Using Detrended Fluctuation Analysis and its Comparison with Other Methods (Multifractal Analysis of Well Log Data)

Dashtian, Hassan | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41338 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Sahimi, Mohammad; Massihi, Mohsen; Jafari, Gholam Reza
  7. Abstract:
  8. One of the main challenges in characterization and simulation of larg scale porous media is spatial heterogeneity and variability of porous media properties such as porosity, density, and lithology at different scales. These information can be achieved at different scale from coring, well logging or seismic data. Well logs are an efficient way to obtain rock and fluid properties of geological patterns specially water resources and hydrocarbon reservoirs. One of the characteristics of geophysical well logs is their complex behavior which seems to imply a multifractal nature.In this study we investigate multifractality and presence of long range correlations in petrophysical well log data such as bulk density (RHOB), natural gamma ray radioactivity (GR), neutron porosity (NPHI) and sonic transient time (DT). Hurst exponents (H) for these spatial series are calculated using Multifractal Random Walk (MRW), Detrended Fluctuation Analysis (DFA) and Power Spectrum method (PS). To quantify a universal fractal scaling exponent for these petrophysical data we use well logs from various wells in southern hydrocarbon reservoirs of Iran where we expect different lithology and depositional environment in their underlying geological structures. Using a generalized DFA method, Multifractal Detrended Fluctuation Analysis (MF-DFA), we study the degrees and sources of multifractality in well log data.We carry out a series of cross-correlation analysis of raw well log data, in order to study the possible connection between natural gamma ray (GR) logs and other types of well logs, such as neutron porosity (NPHI), sonic transient time (denoted usually by DT) and bulk density (RHOB) of oil and gas reservoirs. Three distinct, but complementary, methods are used to analyze the cross correlations, namely, the multifractal detrended cross-correlation analysis (MF-DXA), the so-called Q_cc (m) test in conjunction with the statistical test - the ?^2 (m) distribution - and the cross wavelet transform (XWT) and wavelet coherency
  9. Keywords:
  10. Cross Correlation ; Correlation ; Multifractality ; Well log Data

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