Analyses of the factors influencing sandstone thermal conductivity

Sun, Qiang

doi:10.13168/agg.2017.0001

Cited by 23 publications

(12 citation statements)

References 27 publications

(31 reference statements)

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“…79 Besides, anharmonic scattering plays an important role in the variation of thermal conductivity as a function of temperature. Indeed, at room temperature, the Fe-and Co-modified BT samples exhibit a regular decrease in thermal conductivity with doping, which continues decreasing with increasing temperature, indicating that a phonon−phonon defect 80 prevails in the studied temperature range. Co and Fe co-doped materials indeed have lower thermal conductivities which are less temperature-dependent.…”

Section: Sem Analysis Figurementioning

confidence: 99%

Functionality and Activity of Sol–Gel-Prepared Co and Fe co-Doped Lead-Free BTO for Thermo-Optical Applications

et al. 2023

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The BTO, BFTC, and BCTF compounds were synthesized by the sol–gel method. The XRD study revealed the formation of single-phase tetragonal perovskite structures with the space group (P4mm). The crystalline parameters were studied as a function of Fe and Co contents and occupation of Ba and/or Ti sites by Fe and Co in the BTO lattice. It was found that the obtained strain increases when Ba2+ is substituted by Co2+ and Ti4+ by Fe3+. The Raman investigation confirmed the existence of three active modes (B1/E (TO1LO), (E (TO)/A1(TO3), and (A 1(LO)/E (TO), all of which are related to the existence of the tetragonal phase and strongly support the XRD results. The microstructural study showed a clear correlation between the presence of Fe and Co and the grain size distribution. Optical studies revealed the improvement in band gap energy with transition-metal (Fe and Co) co-doped BTO ceramics. The decrease in the band gap is explained by the competing effects of Columbian interactions, microdeformation, and oxygen defects. The results indicate that the presence of Fe and Co dopants enhances the absorption in the BTO ceramic. The dopants demonstrated an effect on thermal conductivity: they decreased the thermal conductivity of BTO, which is in the range of 0.76–2.23 W m–1 K–1 at room temperature and 2.02–0.27 W m–1 K–1 at elevated temperatures. The microstructure of the manufactured materials and the grain size distribution affect the compressive strength.

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Section: Sem Analysis Figurementioning

confidence: 99%

Functionality and Activity of Sol–Gel-Prepared Co and Fe co-Doped Lead-Free BTO for Thermo-Optical Applications

et al. 2023

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“…Especially in the case of sandstones, the alternative use of textbookderived mean values for thermal modeling is not sufficient for accurate temperature predictions. Sandstones can have a very large range in λ b (e.g., Somerton 1992;Schön 2015), dependent on the variability of controlling rock parameters such as their mineralogical composition, porosity, textural features like detrital grain contacts, grain geometry, bedding, type of cementation, and the type of the pore fluid (e.g., Zimmerman 1989;Clauser and Huenges 1995;Sun et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Pore-fluid-dependent controls of matrix and bulk thermal conductivity of mineralogically heterogeneous sandstones

Kämmlein

Stollhofen

2019

Geotherm Energy

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For a variety of geothermal engineering applications, the only indirectly determinable matrix thermal conductivity (λ m) is frequently used to convert the measured bulk rock thermal conductivity (λ b) of air-saturated sandstones to water-saturated conditions. However, the necessary assumption that the absolute value of λ m remains constant irrespective of the pore fluid present turns out to be not valid in practice and the explicit control factors on λ m have not been demonstrated yet for different pore fluids. A pore fluid-controlled change in the λ m value also questions the transferability of empirical proxy models for the estimation of water-saturated λ b when they were calibrated on air-saturated samples. This study applies a multiple regression analysis to quantitative mineralogical composition data and porosity (Φ) to identify the controls of the λ m for different types of pore fluids (water-vs. air-saturation). In addition, the differences in the calculated λ m values resulting from different calculation methods or input data (theoretical geometric mean model or mineralogical composition data) are examined. We further test the suitability of different sandstone properties as potential proxies for the estimation of the λ b , with respect to the pore fluid type. Differences in the absolute value of λ m of sandstones from different measurement conditions (air-or water-saturated) are most probably related to the formation of authigenic kaolinite in the pore space, originating from the alteration of alkali feldspar. In addition, the thermal properties of the rock matrix are mainly controlled by the volume fractions of the high thermally conductive mineral fractions quartz and dolomite. Empirical models that have solely Φ or P-wave velocity (v p) as variables are not suitable for the prediction of water-saturated λ b of sandstones. Instead, quantitative mineralogical data of high thermally conductive mineral phases such as quartz and dolomite have to be included. The easily measureable v p is proposed as a promising proxy for both pore fluid types tested: combined with the total quartz volume/porosity ratio for air-saturated sandstones, and combined with the quartz plus dolomite volume fractions for water-saturated sandstones.

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“…The TC of rocks can be influenced by other factors such as pressure, temperature, porosity, and fluid saturation [8]. According to the laboratory experiments, 2000 m buried depth can cause only a less than 2% increase in TC, which is within the analytical error of the laboratory testing [9,10], so the pressure has no significant influence on TC in the study area. Therefore, pressure correction was not considered in this paper.…”

Section: Thermal Conductivity Estimationmentioning

confidence: 89%

Thermal Conductivity Estimation Based on Well Logging

Jiang

Wang

et al. 2021

Mathematics

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The thermal conductivity of a stratum is a key factor to study the deep temperature distribution and the thermal structure of the basin. A huge expense of core sampling from boreholes, especially in offshore areas, makes it expensive to directly test stratum samples. Therefore, the use of well logging (the gamma-ray, the neutron porosity, and the temperature) to estimate the thermal conductivity of the samples obtained from boreholes could be a good alternative. In this study, we measured the thermal conductivity of 72 samples obtained from an offshore area as references. When the stratum is considered to be a shale–sand–fluid model, the thermal conductivity can be calculated based on the mixing models (the geometric mean and the square root mean). The contents of the shale and the sand were derived from the natural gamma-ray logs, and the content of the fluid (porosity) was derived from the neutron porosity logs. The temperature corrections of the thermal conductivity were performed for the solid component and the fluid component separately. By comparing with the measured data, the thermal conductivity predicted based on the square root model showed good consistency. This technique is low-cost and has great potential to be used as an application method to obtain the thermal conductivity for geothermal research.

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Analyses of the factors influencing sandstone thermal conductivity

Cited by 23 publications

References 27 publications

Functionality and Activity of Sol–Gel-Prepared Co and Fe co-Doped Lead-Free BTO for Thermo-Optical Applications

Functionality and Activity of Sol–Gel-Prepared Co and Fe co-Doped Lead-Free BTO for Thermo-Optical Applications

Pore-fluid-dependent controls of matrix and bulk thermal conductivity of mineralogically heterogeneous sandstones

Thermal Conductivity Estimation Based on Well Logging

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