Coherent Interpretation of Wideband Electromagnetic Measurements in the Millihertz to Gigahertz Frequency Range
- Nikita Seleznev (Schlumberger-Doll Research Center) | Chang-Yu Hou (Schlumberger-Doll Research Center) | Denise Freed (Schlumberger-Doll Research Center) | Tarek Habashy (Schlumberger-Doll Research Center) | Ling Feng (Schlumberger-Doll Research Center) | Kamilla Fellah (Schlumberger-Doll Research Center) | Guangping Xu (Schlumberger-Doll Research Center and Sandia National Laboratories) | Alexander Nadeev (Schlumberger Reservoir Laboratories)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- June 2018
- Document Type
- Journal Paper
- 334 - 353
- 2018. Society of Petrophysicists & Well Log Analysts
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- 84 since 2007
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Electromagnetic (EM) formation evaluation currently relies on low-frequency resistivity and high-frequency dielectric measurements that are typically not interpreted jointly. In consideration that formation EM responses in different frequency ranges are controlled by different physical phenomena, analysis of a wideband EM response can provide new and complementary sensitivities to formation petrophysical parameters.
We established a wideband rock model to describe the dielectric response of well-sorted clean sandstones in the spectral induced polarization (SIP) frequency range and the dielectric-dispersion frequency range. The model is based on a differential effective-medium approach that accounts for both the Maxwell-Wagner interfacial polarization related to the rock texture and the electric double-layer polarization due to the presence of charged grains. We aim to use a minimal number of parameters in our model to capture the essential dielectric properties in the frequency ranges of interest.
The SIP and dielectric-dispersion spectra were measured on a collection of quarried clean sandstones saturated with brines providing wideband core data. We analyzed these wideband data by applying the rock model simultaneously to the SIP and dielectric spectra. The joint wideband data inversion enabled the estimation of five formation parameters: water-filled porosity, water salinity, cation exchange capacity, dominant grain size, and cementation exponent. The ability to invert for this broad set of formation parameters provides a comprehensive characterization that is unattainable with currently practiced methods. Moreover, when the modeled and measured responses are compatible, the joint wideband inversion of SIP and dielectric-dispersion spectra potentially eliminates interpretation uncertainties if some parameters are independently provided as input.
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