Dielectric Response of Carbonate Core-Plugs – Influence of Heterogeneous Rock Properties on Permittivity

Zhang, Tianhua; Ligneul, P.; Nicot, Benjamin; Pairoys, Fabrice; Akbar, Mahmood

doi:10.2118/136941-ms

Cited by 6 publications

(2 citation statements)

References 9 publications

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“…In particular, Yoshikawa and Overduin (2005) and Watanabe and Wake (2009) studied the freezing characteristics in various saturated and unsaturated soils above and below 0° C, measuring the liquid water content and relative permittivity with NMR and TDR techniques. Zhang et al (2010) and Clennel et al (2007) found that the liquid water content estimated using the expanded mixing model is in agreement with the values measured by NMR for different soil types, water and ice content and temperature.…”

Section: Introductionsupporting

confidence: 64%

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Comparison of GPR and unilateral NMR for water content measurements in a laboratory scale experiment

Ferrara

Tullio

Barone

et al. 2012

Near Surface Geophysics

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Several factors affect antenna‐soil coupling in a Ground Penetrating Radar (GPR) survey, like surface roughness, lithology, lateral heterogeneities, vegetation, antenna height from the surface and water content. Among them, lithology and water content have a direct effect on the bulk electromagnetic properties of the material under investigation. It has been recently pointed out that the wavelet of the early‐time portion of a radar signal is correlated to the shallow subsurface dielectric properties of a material. This result indicates that some information on such properties can be directly extracted from the analysis of GPR early‐time traces. In the present paper, we use the early‐time GPR signal, in terms of average envelope amplitude computed on the first half‐cycle, to map the near‐surface (few centimetres) lateral distribution of dielectric parameters, induced by changing the shallow water content on a concrete slab. This controlled experiment was specifically designed to study the effect of water content variations on antenna‐material coupling, minimizing the influence of both surface roughness and heterogeneity. The quantitative control of the water in the shallow portion of the slab is performed by using a portable unilateral Nuclear Magnetic Resonance (NMR) sensor, which is able to determine the water content in the material on the basis of the measured proton density. The results show a matching pattern of the physical parameters measured with the two different techniques and a very high degree of linear correlation (r = 0.97) between the radar early‐time signal average amplitude and the intensity of the NMR signal, which is proportional to the proton density, i.e., to the water content. This experiment suggests that the early‐time approach could be used as a fast and high‐ spatial resolution tool for qualitatively mapping water content lateral variations in a porous material at shallow depth, using a ground‐coupled single‐offset antenna configuration and that a quantitative evaluation of the moisture content would require a calibration procedure.

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Section: Introductionsupporting

confidence: 64%

“…Zhang et al . () and Clennel et al . () found that the liquid water content estimated using the expanded mixing model is in agreement with the values measured by NMR for different soil types, water and ice content and temperature.…”

Section: Introductionmentioning

confidence: 93%

Comparison of GPR and unilateral NMR for water content measurements in a laboratory scale experiment

Ferrara

Tullio

Barone

et al. 2012

Near Surface Geophysics

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Error Quantification of Dielectric Spectroscopy on Carbonate Core Plugs

et al. 2011

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The recent introduction of a downhole logging device to estimate rock multi-frequency complex permittivity has motivated the development of corresponding laboratory measurements. Various devices for permittivity measurement are described in the literature. Those instruments generally handle powder samples, millimeter-range thin discs or centimeter-range cylindrical plugs. In carbonate rocks, heterogeneity can be observed from micronic to kilometer scales. Laboratory measurements at similar resolution of the downhole tool can provide useful and justifiable input for the interpretation of the logged data. A dielectric device which can measure 1.5 in. diameter and 2.0 in. long core plugs with a large coaxial probe is presented in this paper. The repeatability of the measurements are shown to be within 2% of the material dielectric constant value of dry rock plugs and 3% of wet rock plugs normalized with porosity and salinity. The range of confidence for the inferred cementation factor from dielectric measurements is also quantified and the results show that this cementation factor is not sensitive to the brine salinity. Error bars are displayed over dielectric dispersion curves and used as quality control. Various materials have been tested with this large probe. The measurements on fused quartz, Teflon and ceramic materials match the available published results. Data acquired on pure calcite, dolomite and anhydrite crystals provide a good estimation of the limits of the dielectric properties range for calcium carbonate rocks of complex lithology. In the literature, the properties of these minerals vary over a broad range, which limits their practical use for reservoir characterization. The design of the probe allows averaging the horizontal heterogeneity of the plug, but by flipping the plug upside down the identification of vertical heterogeneity can be put forward. The heterogeneity can be caused by numerous factors such as lithology, pore system, and fluid saturation variations. The case study presented in this paper shows an example of porosity heterogeneity identified by the dielectric spectroscopy measurements, and confirmed by NMR 1D porosity profiling and CT-scan imaging.

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Revisiting Dielectric Logging in Saudi Arabia: Recent Experiences and Applications in Development and Exploration Wells

et al. 2011

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Dielectric logging was introduced in late 70s to mostly measure water filled porosity in the flushed zone independent of water salinity and Archie exponents m and n. Although the technology generated a lot of interest upon its introduction, it eventually disappeared over the years, mostly due to moderate accuracy of the early devices, oversimplified interpretation models and other hardware related complications. Results from extensive field testing of a new generation of dielectric wireline tools indicate that robust and reliable dielectric logging is now feasible in a wide range of environmental conditions and formations. Benchmarking of dielectric measurements against other logs and core data has shown that water-filled porosity can be measured accurately using dielectric logging tools, provided the matrix mineralogy is well defined. Consequently, the technology has gained rapid acceptance in applications involving flushed zone water saturation in environments with variable or unknown salinity, heavy oil identification, and discrimination of non-reservoir rock with high organic content. Dielectric logging is gradually replacing NMR Log-Inject-Log for residual/remaining oil saturation (ROS) measurement, especially in the situations where connate and injected water salinities can be vastly different. Due to the success in ROS applications, most of the recent testing has been focused towards carbonates drilled with water-based-mud. This technology is also being tested in shaly sands and in wells drilled with oil based mud at present. Additional work is underway to accurately characterize dielectric properties of carbonates so as to be able to perform quantitative textural analysis. In shaly sands, high resolution clay volumes and thin bed analysis are challenges that will be addressed in the future.

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Dielectric Response of Carbonate Core-Plugs – Influence of Heterogeneous Rock Properties on Permittivity

Cited by 6 publications

References 9 publications

Comparison of GPR and unilateral NMR for water content measurements in a laboratory scale experiment

Comparison of GPR and unilateral NMR for water content measurements in a laboratory scale experiment

Error Quantification of Dielectric Spectroscopy on Carbonate Core Plugs

Revisiting Dielectric Logging in Saudi Arabia: Recent Experiences and Applications in Development and Exploration Wells

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